Process to produce biofuels from biomass

ABSTRACT

A process for producing biofuels from biomass is provided by removing sulfur compounds and nitrogen compounds from the biomass by contacting the biomass with a digestive solvent to form a pretreated biomass containing soluble carbohydrates and having less than 35% of the sulfur content and less than 35% of the nitrogen content, based on untreated biomass on a dry mass basis, prior to carrying out aqueous phase reforming and further processing to form a liquid fuel.

The present application claims the benefit of U.S. Provisional PatentApplication Ser. No. 61/424,832 filed Dec. 20, 2010, the entiredisclosure of which is hereby incorporated by reference.

FIELD OF THE INVENTION

The invention relates to the production of higher hydrocarbons suitablefor use in transportation fuels and industrial chemicals from biomass.

BACKGROUND OF THE INVENTION

A significant amount of attention has been placed on developing newtechnologies for providing energy from resources other than fossilfuels. Biomass is a resource that shows promise as a fossil fuelalternative. As opposed to fossil fuel, biomass is also renewable.

Biomass may be useful as a source of renewable fuels. One type ofbiomass is plant biomass. Plant biomass is the most abundant source ofcarbohydrate in the world due to the lignocellulosic materials composingthe cell walls in higher plants. Plant cell walls are divided into twosections, primary cell walls and secondary cell walls. The primary cellwall provides structure for expanding cells and is composed of threemajor polysaccharides (cellulose, pectin, and hemicellulose) and onegroup of glycoproteins. The secondary cell wall, which is produced afterthe cell has finished growing, also contains polysaccharides and isstrengthened through polymeric lignin covalently cross-linked tohemicellulose. Hemicellulose and pectin are typically found inabundance, but cellulose is the predominant polysaccharide and the mostabundant source of carbohydrates. However, production of fuel fromcellulose poses a difficult technical problem. Some of the factors forthis difficulty are the physical density of lignocelluloses (like wood)that can make penetration of the biomass structure of lignocelluloseswith chemicals difficult and the chemical complexity of lignocellulosesthat lead to difficulty in breaking down the long chain polymericstructure of cellulose into carbohydrates that can be used to producefuel.

Most transportation vehicles require high power density provided byinternal combustion and/or propulsion engines. These engines requireclean burning fuels which are generally in liquid form or, to a lesserextent, compressed gases. Liquid fuels are more portable due to theirhigh energy density and their ability to be pumped, which makes handlingeasier.

Currently, bio-based feedstocks such as biomass provide the onlyrenewable alternative for liquid transportation fuel. Unfortunately, theprogress in developing new technologies for producing liquid biofuelshas been slow in developing, especially for liquid fuel products thatfit within the current infrastructure. Although a variety of fuels canbe produced from biomass resources, such as ethanol, methanol, andvegetable oil, and gaseous fuels, such as hydrogen and methane, thesefuels require either new distribution technologies and/or combustiontechnologies appropriate for their characteristics. The production ofsome of these fuels also tends to be expensive and raise questions withrespect to their net carbon savings.

Carbohydrates are the most abundant, naturally occurring biomolecules.Plant materials store carbohydrates either as sugars, starches,celluloses, lignocelluloses, hemicelluloses, and any combinationthereof. In one embodiment, the carbohydrates include monosaccharides,polysaccharides or mixtures of monosaccharides and polysaccharides. Asused herein, the term “monosaccharides” refers to hydroxy aldehydes orhydroxy ketones that cannot be hydrolyzed to smaller units. Examples ofmonosaccharides include, but are not limited to, dextrose, glucose,fructose and galactose. As used herein, the term “polysaccharides”refers to saccharides comprising two or more monosaccharide units.Examples of polysaccharides include, but are not limited to, cellulose,sucrose, maltose, cellobiose, and lactose. Carbohydrates are producedduring photosynthesis, a process in which carbon dioxide is convertedinto organic compounds as a way to store energy. The carbohydrates arehighly reactive compounds that can be easily oxidized to generateenergy, carbon dioxide, and water. The presence of oxygen in themolecular structure of carbohydrates contributes to the reactivity ofthe compound. Water soluble carbohydrates react with hydrogen overcatalyst(s) to generate polyols and sugar alcohols, either byhydrogenation, hydrogenolysis or both.

U.S. Publication Nos. 20080216391 and 20100076233 to Cortright et al.describes a process for converting carbohydrates to higher hydrocarbonsby passing carbohydrates through a hydrogenation reaction followed by anAqueous Phase Reforming (“APR”) process. The hydrogenation reactionproduces polyhydric alcohols that can withstand the conditions presentin the APR reaction. Further processing in an APR reaction and acondensation reaction can produce a higher hydrocarbon for use as afuel. Currently APR is limited to feedstocks including sugars orstarches, which competes with the use of these materials for foodresulting in a limited supply. There is a need to directly processbiomass into liquid fuels.

SUMMARY OF THE INVENTION

In an embodiment, a method comprises: (i) providing a biomass containingcelluloses, hemicelluloses, lignin, nitrogen compounds and sulfurcompounds; (ii) removing sulfur compounds and nitrogen compounds fromsaid biomass by contacting the biomass with a digestive solvent to forma pretreated biomass containing carbohydrates and having less than 35%of sulfur content and less than 35% of the nitrogen content untreatedbiomass on a dry mass basis; (iii) contacting the pretreated biomasswith an aqueous phase reforming catalyst to form a plurality ofoxygenated intermediates, and (vi) processing at least a portion of theoxygenated intermediates to form a liquid fuel.

In yet another embodiment, a first portion of the oxygenatedintermediates are recycled to form in part the solvent in step (ii); andprocessing at least a second portion of the oxygenated intermediates toform a liquid fuel.

In yet another embodiment, a method comprises: (i) providing a biomasscontaining celluloses, hemicelluloses, lignin, nitrogen, and sulfurcompounds; (ii) removing sulfur compounds and nitrogen compounds fromsaid biomass by contacting the biomass with a digestive solvent to forma pretreated biomass containing soluble carbohydrates and having lessthan 35% of the sulfur content and less than 35% of the nitrogen contentbased on untreated biomass on a dry mass basis; (iii) contacting atleast a portion of the pretreated biomass with a recycle solvent streamto form a digested portion of the pulp; (iv) contacting at least aportion of the digested portion of the pulp with an aqueous phasereforming catalyst to form a plurality of oxygenated intermediates, and(v) a first portion of the oxygenated intermediates are recycled to formin part the recycle solvent in step (iii), and (vi) processing at leasta second portion of the oxygenated intermediates to form a liquid fuel.

In yet another embodiment, a method comprises: (i) providing a biomasscontaining celluloses, hemicelluloses, lignin, nitrogen, and sulfurcompounds; (ii) removing sulfur compounds and nitrogen compounds fromsaid biomass by contacting the biomass with a digestive solvent to forma pretreated biomass containing soluble carbohydrates and having lessthan 35% of the sulfur content and less than 35% of the nitrogen contentbased on untreated biomass on a dry mass basis; (iii) contacting atleast a portion of the pretreated biomass with a recycle solvent streamto form a digested stream; (iv) contacting at least a portion of thedigested portion of the digested stream with an aqueous phase reformingcatalyst to form a plurality of oxygenated intermediates, (v) a firstportion of the first intermediate stream is recycled to form in part therecycle solvent in step (iii), (vi) contacting at least a portion of thefirst intermediate stream with an aqueous phase reforming catalyst toform a plurality of oxygenated intermediates, and (vii) processing atleast a first portion of the oxygenated intermediates to form a liquidfuel.

In yet another embodiment, a system comprises: a digester that receivesa biomass feedstock and a digestive solvent operating under conditionsto effectively remove nitrogen compounds and sulfur compounds from saidbiomass feedstock and discharges a treated stream comprising acarbohydrate having less than 35% of the sulfur content and less than35% of the nitrogen content based on untreated biomass feedstock on adry mass basis; an aqueous phase reforming reactor comprising an aqueousphase reforming catalyst that receives the treated stream and dischargesan oxygenated intermediate stream, wherein a first portion of theoxygenated intermediate stream is recycled to the digester as at least aportion of the digestive solvent; and a fuels processing reactorcomprising a condensation catalyst that receives a second portion of theoxygenated intermediate stream and discharges a liquid fuel.

In yet another embodiment, a system comprises: a digester that receivesa biomass feedstock and a digestive solvent operating under conditionsto effectively remove nitrogen compounds and sulfur compounds from saidbiomass feedstock and discharges a treated stream comprising acarbohydrate having less than 35% of the sulfur content and less than35% of the nitrogen content based on untreated biomass feedstock on adry mass basis; an aqueous phase reforming reactor comprising an aqueousphase reforming catalyst that receives the treated stream and dischargesan oxygenated intermediate, wherein a first portion of the oxygenatedintermediate stream is recycled to the digester as at least a portion ofthe digestive solvent; a first fuels processing reactor comprising adehydrogenation catalyst that receives a second portion of theoxygenated intermediate stream and discharges an olefin-containingstream; and a second fuels processing reactor comprising an alkylationor olefin oligomerization catalyst that receives the olefin-containingstream and discharges a liquid fuel.

The features and advantages of the invention will be apparent to thoseskilled in the art. While numerous changes may be made by those skilledin the art, such changes are within the spirit of the invention.

BRIEF DESCRIPTION OF THE DRAWING

These drawings illustrate certain aspects of some of the embodiments ofthe invention, and should not be used to limit or define the invention.

FIG. 1 schematically illustrates a block flow diagram of an embodimentof a higher hydrocarbon production process 100A of this invention.

FIG. 2 schematically illustrates a block flow diagram of an embodimentof a higher hydrocarbon production process 100B of this invention.

FIG. 3 schematically illustrates a block flow diagram of an embodimentof a higher hydrocarbon production process 100C of this invention.

FIG. 4 schematically illustrates a block flow diagram of an embodimentof a higher hydrocarbon production process 100D of this invention.

FIG. 5 schematically illustrates a block flow diagram of an embodimentof a higher hydrocarbon production process 100E of this invention.

DETAILED DESCRIPTION OF THE INVENTION

The invention relates to the production of higher hydrocarbons suitablefor use in transportation fuels and industrial chemicals from biomass.The higher hydrocarbons produced are useful in forming transportationfuels, such as synthetic gasoline, diesel fuel, and jet fuel, as well asindustrial chemicals. As used herein, the term “higher hydrocarbons”refers to hydrocarbons having an oxygen to carbon ratio less than theoxygen to carbon ratio of at least one component of the bio-basedfeedstock. As used herein the term “hydrocarbon” refers to an organiccompound comprising primarily hydrogen and carbon atoms, which is alsoan unsubstituted hydrocarbon. In certain embodiments, the hydrocarbonsof the invention also comprise heteroatoms (i.e., oxygen sulfur,phosphorus, or nitrogen) and thus the term “hydrocarbon” may alsoinclude substituted hydrocarbons. The term “soluble carbohydrates”refers to oligosaccharides and monosaccharides that are soluble in thedigestive solvent and that can be used as feedstock to the APR reaction(e.g., pentoses and hexoses).

The methods and systems of the invention have an advantage of convertinga raw biomass feedstock through digestive solvent to digest and remove asubstantial amount of nitrogen compounds, and sulfur compounds containedin the biomass. The nitrogen and sulfur compounds removed can otherwisepoison catalysts used in subsequent processing. The method may alsoremove phosphorus compounds contained in the biomass that canpotentially poison catalysts used in subsequent processing. The treatedbiomass is then converted by aqueous phase reforming reactions to forman oxygenated intermediate stream comprising polyols, alcohols, ketones,aldehydes, and other oxygenated reaction products that can be feddirectly to a processing reaction to form higher hydrocarbons. Theprocess results in an increased conversion and conversion efficiency byminimizing catalyst poisoning and extending catalyst life.

In some embodiments, at least a portion of oxygenated intermediatesproduced in the APR reaction are recycled within the process and systemto at least in part form the in situ generated solvent, which is used inthe biomass digestion process. This recycle saves costs in provision ofa solvent that can be used to extract nitrogen, sulfur, and optionallyphosphorus compounds from the biomass feedstock. Further, by controllingthe degradation of carbohydrate in the APR process, the hydrogenationreaction can be conducted along with the APR reaction at temperaturesranging from 175° C. to 275° C. As a result, a separate hydrogenationreaction section can optionally be avoided, and the fuel formingpotential of the biomass feedstock fed to the process can be increased.This process and reaction scheme described herein also results in acapital cost savings and process operational cost savings. Advantages ofspecific embodiments will be described in more detail below.

In some embodiments, the invention provides methods comprising:providing a biomass feedstock, optionally contacting the biomassfeedstock with a digestive solvent to extract and remove a portion ofthe lignin, and nitrogen, and sulfur compounds, further contacting thebiomass feedstock with a digestive solvent in a digestion system to forman intermediate stream comprising soluble carbohydrates, contacting theintermediate stream with an APR catalyst to form a plurality ofoxygenated intermediates, wherein a first portion of the oxygenatedintermediates are recycled to form the solvent; and contacting at leasta second portion of the oxygenated intermediates with a catalyst to forma liquid fuel.

In reference to FIG. 1, in one embodiment of the invention process 100A,biomass 102 is provided to digestion system 106 that may have one ormore digester(s), whereby the biomass is contacted with a digestivesolvent. The solvent liquor 110, contains dissolved nitrogen compoundsand dissolved sulfur compounds and optionally dissolve phosphoruscompounds, which are removed from the treated biomass pulp 120, suchthat the treated biomass pulp 120 contains solid carbohydrates havingless than 35% of the sulfur content, preferably less than 10% of thesulfur content, and most preferably less than 3% of the sulfur content,and less than 35% of the nitrogen content, preferably less than 10% ofthe nitrogen content, and most preferably less than 3% of the nitrogencontent based on untreated biomass feedstock on a dry mass basis. Atleast a portion of the treated biomass pulp 120 is fed to an aqueousphase reforming system 126 whereby the treated biomass pulp is contactedwith an aqueous reforming catalyst to produce a plurality of oxygenatedintermediates 130, and at least a portion of the oxygenatedintermediates is processed 136 to produce higher hydrocarbons to form aliquid fuel 150.

In reference to FIG. 2, in one embodiment of the invention process 100B,biomass 102 is provided to digestion system 106 that may have one ormore digester(s), whereby the biomass is contacted with a digestivesolvent. The digestive solvent is optionally at least a portion recycledfrom the regenerated chemical liquor stream 168. In such a system atleast a portion of the solvent liquor 110 is processed 160 to regenerateat least a portion of the digestive solvent that is then recycled to thedigestion system. The regeneration and recycle of the chemical liquorvaries depending on the digestive solvent used as some examples arediscussed below. The solvent liquor 162 containing the dissolvednitrogen compounds and dissolved sulfur compounds are removed from thetreated biomass pulp 120 that contains carbohydrates and has less than35% of the sulfur content, preferably less than 10% of the sulfurcontent, and most preferably less than 3% of the sulfur content, andless than 35% of the nitrogen content, preferably less than 10% of thenitrogen content, and most preferably less than 3% of the nitrogencontent based on untreated biomass on a dry mass basis. At least aportion of the treated biomass pulp 120 is fed to an aqueous phasereforming system 126 whereby the treated biomass pulp is contacted withan aqueous reforming catalyst to produce a plurality of oxygenatedintermediates 130, and at least a portion of the oxygenatedintermediates is processed 136 to produce higher hydrocarbons to form aliquid fuel 150. The treated pulp 120 may be optionally washed prior tofeeding to the aqueous phase reforming system 126. If washed, water ismost typically used as wash solvent.

Any suitable (e.g., inexpensive and/or readily available) type ofbiomass can be used. Suitable lignocellulosic biomass can be, forexample, selected from, but not limited to, forestry residues,agricultural residues, herbaceous material, municipal solid wastes,waste and recycled paper, pulp and paper mill residues, and combinationsthereof. Thus, in some embodiments, the biomass can comprise, forexample, corn stover, straw, bagasse, miscanthus, sorghum residue,switch grass, bamboo, water hyacinth, hardwood, hardwood chips, hardwoodpulp, softwood, softwood chips, softwood pulp, and/or combination ofthese feedstocks. The biomass can be chosen based upon a considerationsuch as, but not limited to, cellulose and/or hemicelluloses content,lignin content, growing time/season, growing location/transportationcost, growing costs, harvesting costs and the like.

Prior to treatment with the digestive solvent, the untreated biomass canbe washed and/or reduced in size (e.g., chopping, crushing or debarking)to a convenient size and certain quality that aids in moving the biomassor mixing and impregnating the chemicals from digestive solvent. Thus,in some embodiments, providing biomass can comprise harvesting alignocelluloses-containing plant such as, for example, a hardwood orsoftwood tree. The tree can be subjected to debarking, chopping to woodchips of desirable thickness, and washing to remove any residual soil,dirt and the like.

It is recognized that washing with water prior to treatment withdigestive solvent is desired, to rinse and remove simple salts such asnitrate, sulfate, and phosphate salts which otherwise may be present,and contribute to measured concentrations of nitrogen, sulfur, andphosphorus compounds present. This wash is accomplished at a temperatureof less than about 60 degrees Celsius, and where hydrolysis reactionscomprising digestion do not occur to a significant extent. Othernitrogen, sulfur, and phosphorus compounds are bound to the biomass andare more difficult to remove, and requiring digestion and reaction ofthe biomass, to effect removal. These compounds may be derived fromproteins, amino acids, phospholipids, and other structures within thebiomass, and may be potent catalyst poisons. The removal processdescribed herein, allows removal of some of these more difficult toremove nitrogen and sulfur compounds. In the context of the percentageof nitrogen and sulfur removed in the invention process, it is measuredas percent reduction after treatment compared to a rinsed but untreatedbiomass, whereby the biomass is rinsed with water at ambienttemperature, and referred to as a percent reduction based on “untreatedbiomass on a dry mass basis” or “untreated biomass feedstock on a drymass basis”.

It is also recognized that while nitrogen and sulfur compounds are mostreadily measured in treated and untreated biomass, phosphorous compoundswhich may also serve as catalyst poisons are also likely to be removedduring purification to remove nitrogen and sulfur compounds found inwashed biomass.

In the digestion system, the size-reduced biomass is contacted with thedigestive solvent in at least one digester where the digestion reactiontakes place. The digestive solvent must be effective to digest ligninsand the nitrogen and sulfur compounds, to effect removal of at least aportion of the nitrogen, and sulfur compounds from the biomass.

In one aspect of the embodiment, the digestive solvent maybe aKraft-like digestive solvent that contains (a) at least 0.5 wt %, morepreferably at least 4 wt %, to 20 wt %, more preferably to 10 wt %,based on the digestive solvent, of at least one alkali selected from thegroup consisting of sodium hydroxide, sodium carbonate, sodium sulfide,potassium hydroxide, potassium carbonate, ammonium hydroxide, andmixtures thereof, (b) optionally, 0 to 3%, based on the digestivesolvent, of anthraquinone, sodium borate and/or polysulfides; and (c)water (as remainder of the digestive solvent). In some embodiments, thedigestive solvent may have an active alkali of between 5 to 25%, morepreferably between 10 to 20%. The term “active alkali” (AA), as usedherein, is a percentage of alkali compounds combined, expressed assodium oxide based on weight of the biomass less water content (drysolid biomass). If sodium sulfide is present in the digestive solvent,the sulfidity can range from about 15% to about 40%, preferably fromabout 20 to about 30%. The term “sulfidity”, as used herein, is apercentage ratio of Na2S, expressed as Na2O, to active alkali. digestivesolvent to biomass ratio can be within the range of 0.5 to 50,preferably 2 to 10. The digestion is carried out typically at a cookingliquor to biomass ratio in the range of 2 to 6, preferably 3 to 5. Thedigestion reaction is carried out at a temperature within the range of60° C. to 230° C., preferably 80 to 180 C, and a residence time within0.25 h to 24 h. The reaction is carried out under conditions effectiveto provide a digested biomass stream containing digested biomass havinga lignin content of 1% to 20% by weight, based on the digested biomass,and a chemical liquor stream containing alkali compounds and dissolvedlignin and hemicelluloses material.

The digester can be, for example, a pressure vessel of carbon steel orstainless steel or similar alloy. The digestion system can be carriedout in the same vessel or in a separate vessel. The cooking can be donein continuous or batch mode. Suitable pressure vessels include, but arenot limited to the “PANDIATM Digester” (Voest-Alpine IndustrienlagenbauGmbH, Linz, Austria), the “DEFIBRATOR Digester” (Sunds Defibrator ABCorporation, Stockholm, Sweden), M&D (Messing & Durkee) digester (BauerBrothers Company, Springfield, Ohio, USA) and the KAMYR Digester(Andritz Inc., Glens Falls, N.Y., USA). The digestive solvent has a pHfrom 10 to 14, preferably around 12 to 13 depending on AA. The contentscan be kept at a temperature within the range of from 100° C. to 230° C.for a period of time, more preferably within the range from about 130°C. to about 180° C. The period of time can be from about 0.25 to 24.0hours, preferably from about 0.5 to about 2 hours, after which thepretreated contents of the digester are discharged. For adequatepenetration, a sufficient volume of liquor is required to ensure thatall the biomass surfaces are wetted. Sufficient liquor is supplied toprovide the specified digestive solvent to biomass ratio. The effect ofgreater dilution is to decrease the concentration of active chemical andthereby reduce the reaction rate.

In a system using the digestive solvent such as a Kraft-like digestivesolvent similar to those used in a Kraft pulp and paper process, thechemical liquor may be regenerated in a similar manner to a Kraft pulpand paper chemical regeneration process. For example, in reference toFIG. 2 when used in a Kraft-like digestive solvent system, therecaustisized chemical recycle stream 168 obtained by regenerating atleast a portion of the solvent liquor stream through a chemicalregeneration system 160. In an embodiment, chemical liquor stream isobtained by concentrating at least a portion of the solvent liquorstream 110 in a concentration system thereby producing a concentratedchemical liquor stream then burning the concentrated chemical liquorstream in a boiler system thereby producing chemical recycle stream 168and a flue gas stream then converting the sodium containing compounds tosodium hydroxide in the recaustisizing system by contacting with lime(CaO) producing the recaustisized chemical recycle stream 168 that canbe used as a portion of the digestive solvent containing sodiumhydroxide.

In another embodiment, an at least partially water miscible organicsolvent that has partial solubility in water, preferably greater than 2weight percent in water, may be used as digestive solvent to aid indigestion of lignin, and the nitrogen, and sulfur compounds. In one suchembodiment, the digestive solvent is a water-organic solvent mixturewith optional inorganic acid promoters such as HCl or sulfuric acid.Oxygenated solvents exhibiting full or partial water solubility arepreferred digestive solvents. In such a process, the organic digestivesolvent mixture can be, for example, methanol, ethanol, acetone,ethylene glycol, triethylene glycol and tetrahydrofufuryl alcohol.Organic acids such as acetic, oxalic, acetylsalicylic and salicylicacids can also be used as catalysts (as acid promoter) in the at leastpartially miscible organic solvent process. Temperatures for thedigestion may range from about 130 to about 220 degrees Celsius,preferably from about 140 to 180 degrees Celsius, and contact times from0.25 to 24 hours, preferably from about one to 4 hours. Preferably, apressure from about 250 kPa to 7000 kPa, and most typically from 700 kPato 3500 kPa, maintained on the system to avoid boiling or flashing awayof the solvent.

Optionally the pretreated biomass stream can be washed prior to aqueousreforming. In the wash system, the pretreated biomass stream can bewashed to remove one or more of non-cellulosic material, non-fibrouscellulosic material, and non-degradable cellulosic material prior toaqueous phase reforming. The pretreated biomass stream is washed withwater stream under conditions to remove at least a portion of lignin andhemicellulosic material in the pretreated biomass stream and producingwashed pretreated biomass stream having solids content of 5% to 15% byweight, based on the washed pretreated biomass stream. For example, thepretreated biomass stream can be washed with water to remove dissolvedsubstances, including degraded, but non-processable cellulose compounds,solubilised lignin, and/or any remaining alkaline chemicals such assodium compounds that were used for cooking or produced during thecooking (or pretreatment). The washed digested biomass stream maycontain higher solids content by further processing such as mechanicaldewatering as described below.

In a preferred embodiment, the pretreated biomass stream is washedcounter-currently. The wash can be at least partially carried out withinthe digester and/or externally with separate washers. In one embodimentof the invention process, the wash system contains more than one washsteps, for example, first washing, second washing, third washing, etc.that produces washed pretreated biomass stream from first washing,washed digested biomass stream from second washing, etc. operated in acounter current flow with the water, that is then sent to subsequentprocesses as washed pretreated biomass stream. The water is recycledthrough first recycled wash stream and second recycled wash stream andthen to third recycled wash stream. Water recovered from the chemicalliquor stream by the concentration system can be recycled as wash waterto wash system. It can be appreciated that the washed steps can beconducted with any number of steps to obtain the desired washed digestedbiomass stream. Additionally, the washing may adjust the pH forsubsequent steps where the pH is about 2.0 to 10.0, where optimal pH isdetermined by the catalyst employed in the APR step. Bases such asalkali base may be optionally added, to adjust pH.

In some embodiments, the reactions described are carried out in anysystem of suitable design, including systems comprising continuous-flow,batch, semi-batch or multi-system vessels and reactors. One or morereactions or steps may take place in an individual vessel and theprocess is not limited to separate reaction vessels for each reaction ordigestion. In some embodiments the system of the invention utilizes afluidized catalytic bed system. Preferably, the invention is practicedusing a continuous-flow system at steady-state equilibrium.

In reference to FIG. 3, in one embodiment of the invention process 100C,biomass 102 is provided to digestion system 106 that may have one ormore digester(s), whereby the biomass is contacted with a digestivesolvent. The digestive solvent is optionally at least a portion recycledfrom the APR reaction as an recycle stream 128. The APR recycle stream128 can comprise a number of components including in situ generatedsolvents, which may be useful as digestive solvent at least in part orin entirety. The term “in situ” as used herein refers to a componentthat is produced within the overall process; it is not limited to aparticular reactor for production or use and is therefore synonymouswith an in-process generated component. The in situ generated solventsmay comprise oxygenated intermediates. The digestive process to removenitrogen, and sulfur compounds may vary within the reaction media sothat a temperature gradient exists within the reaction media, allowingfor nitrogen, and sulfur compounds to be extracted at a lowertemperature than cellulose. For example, the reaction sequence maycomprise an increasing temperature gradient from the biomass feedstock102. The non-extractable solids may be removed from the reaction as anoutlet stream 120. The treated biomass stream 120 is an intermediatestream that may comprise the treated biomass at least in part in theform of carbohydrates. The composition of the intermediate carbohydratestream 120 may vary and may comprise a number of different compounds.Preferably, the carbohydrates have 2 to 12 carbon atoms, and even morepreferably 2 to 6 carbon atoms. The carbohydrates may also have anoxygen to carbon ratio from 0.5:1 to 1:1.2. At least a portion of thedigested portion of the pulp 120 is fed to a hydrogenolysis system 126whereby at least a portion of the digested pulp is contacted with anaqueous reforming catalyst to produce a plurality of oxygenatedintermediates 130. A first portion of the oxygenated intermediate stream128 is recycled to digester 106. A second portion of the oxygenatedintermediates is processed 136 to produce higher hydrocarbons to form aliquid fuel 150.

In reference to FIG. 4, in one embodiment of the invention process 100D,biomass 102 is provided to digestion system 106 that may have one ormore digester(s), whereby the biomass is contacted with a digestivesolvent. The solvent liquor 110 containing the dissolved nitrogencompounds and dissolved sulfur compounds and at least a portion of thelignin are removed from the treated biomass pulp 120 that containscarbohydrates and having less than 35% of sulfur content, preferablyless than 10% of sulfur content, and most preferably less than 3% ofsulfur content, and less than 35% nitrogen content, preferably less than10% of nitrogen content, and most preferably less than 3% of nitrogencontent, based on the nitrogen content or sulfur content, respectively,of the untreated biomass 102 on a dry mass basis. At least a portion ofthe treated biomass pulp 120 is fed to a first zone of an aqueous phasereforming system 126A, whereby the treated biomass pulp is contactedwith a recycle solvent stream 124. Undigested portion of the pulp from126A is discharged as undigested solids stream 125. At least a portionof the digested portion of the pulp from 126A, 122, is provided to asecond zone of an aqueous phase reforming system 126B whereby thedigested portion of the pulp is contacted with an aqueous reformingcatalyst to produce a plurality of oxygenated intermediates. A firstportion of the oxygenated intermediate stream 124 is recycled to thefirst zone of the aqueous phase reforming system 126A. A second portionof the oxygenated intermediates 130 is processed 136 to produce higherhydrocarbons to form a liquid fuel 150. A precipitate solids stream 127,containing some of the lignin, produced upon separation of the firstportion of the oxygenated intermediates stream that is recycled 124, isdischarged. The treated pulp 120 may be optionally washed prior tofeeding to the first zone aqueous phase reforming system 126A. Ifwashed, water is most typically used as wash solvent. The aqueous phasereforming system 126A and 126B may be carried out in the vessel in aseparate zone or in a separate vessel.

In reference to FIG. 5, in one embodiment of the invention process 100E,biomass 102 is provided to digestion system 106 that may have one ormore digester(s), whereby the biomass is contacted with a digestivesolvent. The solvent liquor 110 containing the dissolved nitrogencompounds and dissolved sulfur compounds and at least a portion of thelignin are removed from the treated biomass pulp 120 that containscarbohydrates and having less than 35% of the sulfur content, preferablyless than 10% of the sulfur content, and most preferably less than 3% ofthe sulfur content, and less than 35% of the nitrogen content,preferably less than 10% of the nitrogen content, and most preferablyless than 3% of the nitrogen content, based on the nitrogen content orsulfur content, respectively, of the untreated biomass 102 on a dry massbasis. At least a portion of the treated biomass pulp 120 is fed to afirst digestive zone of an aqueous reforming system 126A, whereby thetreated biomass pulp is contacted with a recycle first intermediatessolvent stream 124, and an optional monooxygenates solvent stream 128 toproduce digested stream 122 and a undigested pulp 125. Undigestedportion of the pulp from 126A is discharged as undigested solids stream125. At least a portion of the digested portion of the pulp from 126Acomprises stream 122, and is provided to a second zone of an aqueousreforming system 126B whereby the digested portion of the pulp iscontacted with an aqueous reforming catalyst or with a hydrogenolysiscatalyst optionally in the presence of external hydrogen source toproduce a first intermediates stream 123, containing diols and polyolsand sugar alcohols, and some monooxygenates. A first portion of thefirst oxygenated intermediate stream 124 is recycled to the first zoneof the aqueous reforming system 126A. A second portion of the oxygenatedintermediates is processed via 126C whereby the soluble intermediatesstream is provided to a third zone of an aqueous reforming system 126Cwhereby the soluble intermediates stream is contacted with an aqueousreforming catalyst to produce a plurality of oxygenated intermediates130 containing monooxygenates. A first portion of the oxygenatedintermediates is processed 136 to produce higher hydrocarbons to form aliquid fuel 150. A second portion of the oxygenated intermediate streamis optionally recycled back 128 to digestive zone 126A, to provideadditional solvent for digestion of the treated pulp 120. Precipitatesolids streams 127 and 129 containing some of the lignin, are optionallyproduced by cooling of the reactor products or removing a portion of theoxygenated solvents from 126B and 126C, respectively. The treated pulp120 may be optionally washed prior to feeding to the first zone aqueousphase reforming system 126A. If washed, water is most typically used aswash solvent. The aqueous reforming system 126A, 126B, and 126C may becarried out in the vessel in a separate zone or in a separate vessel.

Use of separate processing zones for steps 126B and 126C allowsconditions to be optimized for digestion and hydrogenation or aqueousreforming of the digested pulp components in 126B, independent fromoptimization of the conversion of oxygenated intermediates tomonooxygenates in 126C, before feeding to step 136 to make higherhydrocarbon fuels. A lower reaction temperature in 126B may beadvantageous to minimize heavy ends byproduct formation, by conductingthe hydrogenation and hydrogenolysis steps initially at a lowtemperature. This has been observed to result in an intermediates streamwhich is rich in diols and polyols, but essentially free ofnon-hydrogenated monosaccharides which otherwise would serve as heavyends precursors. The subsequent conversion in 126C of mostly solubilizedintermediates can be done efficiently at a higher temperature, whereresidence time is minimized to avoid the undesired continued reaction ofmonooxygenates to form alkane or alkene byproducts. In this manner,overall yields to desired monooxygenates may be improved, via conductingthe conversion in two or more stages.

Use of separate processing zones for steps 126B and 126C allowsconditions to be optimized for digestion and aqueous phase reforming ofthe digested pulp components in 126B, independent from optimization ofthe conversion of oxygenated intermediates to mono-oxygenates in 126C,before feeding to step 136 to make higher hydrocarbon fuels. A lowerreaction temperature in 126B may be advantageous to minimize heavy endsbyproduct formation, by conducting the aqueous phase reforming reactionstep initially at a low temperature. This has been observed to result inan intermediates stream which is rich in diols and polyols, butessentially free of non-hydrogenated monosaccharides which otherwisewould serve as heavy ends precursors. The subsequent conversion in 126Cof mostly solubilized intermediates can be done efficiently at a highertemperature, where residence time is minimized to avoid the undesiredcontinued reaction of monooxygenates to form alkane or alkene byproductsIn this manner, overall yields to desired monooxygenates may beimproved, via conducting the conversion in two or more stages.

Various factors affect the extraction of sulfur compounds and nitrogencompounds of the biomass feedstock in the extractive process. In someembodiments, hemicellulose along with nitrogen, phosphorus and sulfurcompounds may be extracted from the biomass feedstock with a digestivesolvent.

Nitrogen, phosphorus and sulfur compounds extraction begins above 100°C., with solubilization and hydrolysis becoming complete at temperaturesaround 170° C., aided by organic acids (e.g., carboxylic acids) formedfrom partial degradation of carbohydrate components. Some lignins can besolubilized before cellulose, while other lignins may persist to highertemperatures. Organic, in situ generated solvents, which may comprise aportion of the oxygenated intermediates, including, but not limited to,light alcohols and polyols, can assist in solubilization and extractionof lignin and other components.

At temperatures above about 120° C., carbohydrates can degrade through aseries of complex self-condensation reactions to form caramelans, whichare considered degradation products that are difficult to convert tofuel products. In general, some degradation reactions can be expectedwith aqueous reaction conditions upon application of temperature, giventhat water will not completely suppress oligomerization andpolymerization reactions.

In some embodiments of the invention, nitrogen and sulfur compounds areremoved from the biomass feedstock in a digestive solvent medium by atleast a partial hydrolysis such as, including, but not limited to, theKraft type process and organic-solvent assisted process described aboveand acid hydrolysis and other biomass hydrolysis processes that canpartially digest the biomass and extract nitrogen and sulfur compoundsto be separated from the solid biomass (pulp). In certain embodiments,the hydrolysis reaction can occur at a temperature between 20° C. and250° C. and a pressure between 1 bar and 100 bar. An enzyme may be usedfor hydrolysis at low temperature and pressure. In embodiments includingstrong acid and enzymatic hydrolysis, the hydrolysis reaction can occurat temperatures as low as ambient temperature and pressure between 1 bar(100 kPa) and 100 bar (10,100 kPa). In some embodiments, the hydrolysisreaction may comprise a hydrolysis catalyst (e.g., a metal or acidcatalyst) to aid in the hydrolysis reaction. The catalyst can be anycatalyst capable of effecting a hydrolysis reaction. For example,suitable catalysts can include, but are not limited to, acid catalysts,base catalysts, metal catalysts, and any combination thereof. Acidcatalysts can include organic acids such as acetic, formic, levulinicacid, and any combination thereof. In an embodiment the acid catalystmay be generated in the APR reaction and comprise a component of theoxygenated intermediate stream.

In some embodiments, the digestive solvent may contain an in situgenerated solvent. The in situ generated solvent generally comprises atleast one alcohol or polyol capable of solvating some of the sulfurcompounds, and nitrogen compounds of the biomass feedstock. For example,an alcohol may be useful for solvating nitrogen, sulfur, and optionallyphosphorus compounds, and in solvating lignin from a biomass feedstockfor use within the process. The in situ generated solvent may alsoinclude one or more organic acids. In some embodiments, the organic acidcan act as a catalyst in the removal of nitrogen and sulfur compounds bysome hydrolysis of the biomass feedstock. Each in situ generated solventcomponent may be supplied by an external source, generated within theprocess, and recycled to the hydrolysis reactor, or any combinationthereof. For example, a portion of the oxygenated intermediates producedin the APR reaction may be separated in the separator stage for use asthe in situ generated solvent in the hydrolysis reaction. In anembodiment, the in situ generated solvent can be separated, stored, andselectively injected into the recycle stream so as to maintain a desiredconcentration in the recycle stream.

Each reactor vessel of the invention preferably includes an inlet and anoutlet adapted to remove the product stream from the vessel or reactor.In some embodiments, the vessel in which at least some digestion occursmay include additional outlets to allow for the removal of portions ofthe reactant stream. In some embodiments, the vessel in which at leastsome digestion occurs may include additional inlets to allow foradditional solvents or additives.

The digestion step may occur in any contactor suitable for solid-liquidcontacting. The digestion may for example be conducted in a single ormultiple vessels, with biomass solids either fully immersed in liquiddigestive solvent, or contacted with solvent in a trickle bed or piledigestion mode. As a further example, the digestion step may occur in acontinuous multizone contactor as described in U.S. Pat. No. 7,285,179(Snekkenes et al., “Continuous Digester for Cellulose Pulp includingMethod and Recirculation System for such Digester”), which is herebyincorporated by reference. Alternately, the digestion may occur in afluidized bed or stirred contactor, with suspended solids. The digestionmay be conducted batchwise, in the same vessel used for pre-wash, postwash, and/or subsequent reaction steps.

The relative composition of the various carbohydrate components in thetreated biomass stream affects the formation of undesirable by-productssuch as coke in the APR reaction. In particular, a low concentration ofcarbohydrates present as reducing sugars, or containing free aldehydegroups, in the treated biomass stream can minimize the formation ofunwanted by-products. In preferred embodiments, it is desirable to havea concentration of no more than 5 wt %, based upon total liquid, ofreadily degradable carbohydrates or heavy end precursors in the treatedbiomass, while maintaining a total organic intermediates concentration,which can include the oxygenated intermediates (e.g., mono-oxygenates,diols, and/or polyols) derived from the carbohydrates, as high aspossible, via use of concerted reaction or rapid recycle of the liquidbetween the digestion zone, and a catalytic reaction zone converting thesolubilized carbohydrates to oxygenated intermediates.

For any of the configurations 100A through D, a substantial portion oflignin is removed with solvent 110 from digesting step 106. Inconfiguration, the remaining lignin, if present, can be removed uponcooling or partial separation of oxygenates from APR product stream 130,to comprise a precipitated solids stream 131 as shown for 100D in FIG.4. Optionally, the precipitated solids stream containing lignin may beformed by cooling the digested solids stream 129 prior to APR reaction126. In yet another configuration, the lignin which is not removed withdigestion solvent 110 is passed into step 136, where it may beprecipitated upon vaporization or separation of APR product stream 130,during processing to product higher hydrocarbons stream 150.

Aqueous phase reforming (APR) converts polyhydric alcohols to carbonylsand/or aldehydes, which react over a catalyst with water to formhydrogen, carbon dioxide, and oxygenated intermediates, which comprisesmaller alcohols (e.g., monohydric and/or polyhydric alcohols) such as,for example, disclosed in U.S. Publication Nos. 20080216391 whichdisclosure is herein incorporated by reference. The alcohols can furtherreact through a series of deoxygenation reactions to form additionaloxygenated intermediates that can produce higher hydrocarbons through aprocessing reaction such as a condensation reaction.

Referring again to FIG. 1, according to one embodiment, the treatedbiomass stream 120 from the removal system 106 can be passed to an APRreaction to produce oxygenated intermediates. The treated biomass stream120 may comprise C5 and C6 carbohydrates that can be reacted in the APRreaction. For embodiments comprising thermocatalytic APR, oxygenatedintermediates such as sugar alcohols, sugar polyols, carboxylic acids,ketones, and/or furans can be converted to fuels in a further processingreaction. The APR reaction can comprise an APR catalyst to aid in thereactions taking place. The APR reaction conditions can be such that anAPR reaction can take place along with a hydrogenation reaction, ahydrogenolysis reaction, or hydro-deoxygenation reaction, or alltogether as many of the reaction conditions overlap or arecomplimentary. The various reactions can result in the formation of oneor more oxygenated intermediate streams 130. As used herein, an“oxygenated intermediate” can include one or more polyols, alcohols,ketones, or any other hydrocarbon having at least one oxygen atom.

In some embodiments, the APR catalysts can be a heterogeneous catalystcapable of catalyzing a reaction between hydrogen and carbohydrate,oxygenated intermediate, or both to remove one or more oxygen atoms toproduce in-situ hydrogen for APR and to produce alcohols and polyols tobe fed to the condensation reactor. The APR catalyst can generallyinclude Cu, Re, Ni, Fe, Co, Ru, Pd, Rh, Pt, Os, Ir, Sn, and alloys orany combination thereof, either alone or with promoters such as W, Mo,Au, Ag, Cr, Zn, Mn, B, P, Bi, and alloys or any combination thereof.Other effective APR catalyst materials include either supported nickelor ruthenium modified with rhenium. In some embodiments, the APRcatalyst also includes any one of the supports, depending on the desiredfunctionality of the catalyst. The APR catalysts may be prepared bymethods known to those of ordinary skill in the art. In some embodimentsthe APR catalyst includes a supported Group VIII metal catalyst and ametal sponge material (e.g., a sponge nickel catalyst). Raney nickelprovides an example of an activated sponge nickel catalyst suitable foruse in this invention. In some embodiments, the APR reaction in theinvention is performed using a catalyst comprising a nickel-rheniumcatalyst or a tungsten-modified nickel catalyst. One example of asuitable catalyst for the APR reaction of the invention is acarbon-supported nickel-rhenium catalyst.

In some embodiments, a suitable Raney nickel catalyst may be prepared bytreating an alloy of approximately equal amounts by weight of nickel andaluminum with an aqueous alkali solution, e.g., containing about 25weight % of sodium hydroxide. The aluminum is selectively dissolved bythe aqueous alkali solution resulting in a sponge shaped materialcomprising mostly nickel with minor amounts of aluminum. The initialalloy includes promoter metals (e.g., molybdenum or chromium) in theamount such that 1 to 2 weight % remains in the formed sponge nickelcatalyst. In another embodiment, the APR catalyst is prepared using asolution of ruthenium(III) nitrosylnitrate, ruthenium (III) chloride inwater to impregnate a suitable support material. The solution is thendried to form a solid having a water content of less than 1% by weight.The solid is then reduced at atmospheric pressure in a hydrogen streamat 300° C. (uncalcined) or 400° C. (calcined) in a rotary ball furnacefor 4 hours. After cooling and rendering the catalyst inert withnitrogen, 5% by volume of oxygen in nitrogen is passed over the catalystfor 2 hours.

In certain embodiments, the APR catalyst may include a catalyst support.The catalyst support stabilizes and supports the catalyst. The type ofcatalyst support used depends on the chosen catalyst and the reactionconditions. Suitable supports for the invention include, but are notlimited to, carbon, silica, silica-alumina, zirconia, titania, ceria,vanadia, nitride, boron nitride, heteropolyacids, hydroxyapatite, zincoxide, chromia, zeolites, carbon nanotubes, carbon fullerene and anycombination thereof.

The conditions for which to carry out the APR reaction will vary basedon the type of starting material and the desired products. In general,the APR reaction is conducted at temperatures of 80° C. to 300° C., andpreferably at 120° C. to 300° C., and most preferably at 200° C. to 280°C. In some embodiments, the APR reaction is conducted at pressures from500 kPa to 14000 kPa.

The APR reaction can optionally be conducted with pre-addition of afraction of the hydrogen required for conversion, to facilitatehydrogenation reactions which are advantageous in converting speciescontaining less stable carbonyl groups such as monosaccharides to morestable alcohols such as sugar alcohols. The hydrogen may be suppliedfrom an external source, or via recycle of excess hydrogen formed in theAPR reaction section, after initiation of the reaction sequence.

The hydrogen used in the hydrogenolysis reaction of the currentinvention can include external hydrogen, recycled hydrogen, in situgenerated hydrogen, and any combination thereof.

In an embodiment, the use of a hydrogenolysis reaction may produce lesscarbon dioxide and a greater amount of polyols than a reaction thatresults in reforming of the reactants. For example, reforming can beillustrated by formation of isopropanol (i.e., IPA, or 2-propanol) fromsorbitol:C6H14O6+H2O→4H2+3CO2+C3H8O;dHR=−40 kJ/g-mol  (Eq. 1)

Alternately, in the presence of hydrogen, polyols and mono-oxygenatessuch as IPA can be formed by hydrogenolysis, where hydrogen is consumedrather than produced:C6H14O6+3H2→2H2O+2C3H8O2;dHR=+81 kJ/gmol  (Eq. 2)C6H14O6+5H2→4H2O+2C3H8O;dHR=−339 kJ/gmol  (Eq. 3)

As a result of the differences in the reaction conditions (e.g.,presence of hydrogen), the products of the hydrogenolysis reaction maycomprise greater than 25% by mole, or alternatively, greater than 30% bymole of polyols, which may result in a greater conversion in asubsequent processing reaction. In addition, the use of a hydrolysisreaction rather than a reaction running at reforming conditions mayresult in less than 20% by mole, or alternatively less than 30% by molecarbon dioxide production. As used herein, “oxygenated intermediates”generically refers to hydrocarbon compounds having one or more carbonatoms and between one and three oxygen atoms (referred to herein asC₁₊O₁₋₃ hydrocarbons), such as polyols and smaller molecules (e.g., oneor more polyols, alcohols, ketones, or any other hydrocarbon having atleast one oxygen atom).

In an embodiment, hydrogenolysis is conducted under neutral or acidicconditions, as needed to accelerate hydrolysis reactions in addition tothe hydrogenolysis. Hydrolysis of oligomeric carbohydrates may becombined with hydrogenation to produce sugar alcohols, which can undergohydrogenolysis.

A second aspect of hydrogenolysis entails the breaking of —OH bonds suchas:RC(H)₂—OH+H₂→RCH₃+H₂O

This reaction is also called “hydrodeoxygenation”, and may occur inparallel with C—C bond breaking hydrogenolysis. Diols may be convertedto mono-oxygenates via this reaction. As reaction severity is increasedby increases in temperature or contact time with catalyst, theconcentration of polyols and diols relative to mono-oxygenates willdiminish, as a result of this reaction. Selectivity for C—C vs. C—OHbond hydrogenolysis will vary with catalyst type and formulation. Fullde-oxygenation to alkanes can also occur, but is generally undesirableif the intent is to produce mono-oxygenates or diols and polyols whichcan be condensed or oligomerized to higher molecular weight fuels, in asubsequent processing step. Typically, it is desirable to send onlymono-oxygenates or diols to subsequent processing steps, as higherpolyols can lead to excessive coke formation on condensation oroligomerization catalysts, while alkanes are essentially unreactive andcannot be combined to produce higher molecular weight fuels.

The APR product stream 130 may comprise APR products that includeoxygenated intermediates. As used herein, “oxygenated intermediates”generically refers to hydrocarbon compounds having one or more carbonatoms and between one and three oxygen atoms (referred to herein asC₁₊O₁₋₃ hydrocarbons), such as ketones, aldehydes, furans, hydroxycarboxylic acids, carboxylic acids, alcohols, diols and triols.Preferably, the oxygenated intermediates have from one to six carbonatoms, or two to six carbon atoms, or three to six carbon atoms. Theketones may include, without limitation, hydroxyketones, cyclic ketones,diketones, acetone, propanone, 2-oxopropanal, butanone,butane-2,3-dione, 3-hydroxybutane-2-one, pentanone, cyclopentanone,pentane-2,3-dione, pentane-2,4-dione, hexanone, cyclohexanone,2-methyl-cyclopentanone, heptanone, octanone, nonanone, decanone,undecanone, dodecanone, methylglyoxal, butanedione, pentanedione,diketohexane, and isomers thereof. The aldehydes may include, withoutlimitation, hydroxyaldehydes, acetaldehyde, propionaldehyde,butyraldehyde, pentanal, hexanal, heptanal, octanal, nonal, decanal,undecanal, dodecanal, and isomers thereof. The carboxylic acids mayinclude, without limitation, formic acid, acetic acid, propionic acid,butanoic acid, pentanoic acid, hexanoic acid, heptanoic acid, isomersand derivatives thereof, including hydroxylated derivatives, such as2-hydroxybutanoic acid and lactic acid. Alcohols may include, withoutlimitation, primary, secondary, linear, branched or cyclic C1+ alcohols,such as methanol, ethanol, n-propyl alcohol, isopropyl alcohol, butylalcohol, isobutyl alcohol, butanol, pentanol, cyclopentanol, hexanol,cyclohexanol, 2-methyl-cyclopentanonol, heptanol, octanol, nonanol,decanol, undecanol, dodecanol, and isomers thereof. The diols mayinclude, without limitation, ethylene glycol, propylene glycol,1,3-propanediol, butanediol, pentanediol, hexanediol, heptanediol,octanediol, nonanediol, decanediol, undecanediol, dodecanediol, andisomers thereof. The triols may include, without limitation, glycerol,1,1,1 tris(hydroxymethyl)-ethane (trimethylolethane),trimethylolpropane, hexanetriol, and isomers thereof. In an embodiment,any alcohols, diols, triols are dehydrogenated in a dehydrogenationreaction to produce a carbonyl useful in an aldol condensation reaction.Furans and furfurals include, without limitation, furan,tetrahydrofuran, dihydrofuran, 2-furan methanol,2-methyl-tetrahydrofuran, 2,5-dimethyl-tetrahydrofuran, 2-methyl furan,2-ethyl-tetrahydrofuran, 2-ethyl furan, hydroxylmethylfurfural,3-hydroxytetrahydrofuran, tetrahydro-3-furanol, 2,5-dimethyl furan,5-hydroxymethyl-2(5H)-furanone,dihydro-5-(hydroxymethyl)-2(3H)-furanone, tetrahydro-2-furoic acid,dihydro-5-(hydroxymethyl)-2(3H)-furanone, tetrahydrofurfuryl alcohol,1-(2-furyl)ethanol, hydroxymethyltetrahydrofurfural, and isomersthereof.

The oxygenated intermediate stream may generally be characterized ascomprising components corresponding to the formula: CnOmHx. In anembodiment, n=1-6 and m=1 to 6, m≦n, and x is an integer that completesthe molecular structure (e.g., between 1 and 2n+2). Other elements suchas nitrogen, phosphorus or sulfur may also be present in thesemolecules. Additional components that may be present in the APR productsstream can include hydrogen and other gases such as carbon dioxide.These components can be separated from the oxygenated intermediates orthey can be fed to the condensation reaction for removal after thecondensation reaction.

The oxygenated intermediate stream 130 may then pass from the APRreaction to a further processing stage 136. In some embodiments,optional separation stage includes elements that allow for theseparation of the oxygenated intermediates into different components. Insome embodiments of the present invention, the separation stage canreceive the oxygenated intermediate stream 130 from the APR reaction andseparate the various components into two or more streams. For example, asuitable separator may include, but is not limited to, a phaseseparator, stripping column, extractor, filter, or distillation column.In some embodiments, a separator is installed prior to a processingreaction to favor production of higher hydrocarbons by separating thehigher polyols from the oxygenated intermediates. In such an embodiment,the higher polyols can be recycled back through to the APR reaction,while the other oxygenated intermediates are passed to the processingreaction 136. In addition, an outlet stream from the separation stagecontaining a portion of the oxygenated intermediates may act as in situgenerated digestive solvent when recycled to the removal reactor ordigester 106. In one embodiment, the separation stage can also be usedto remove some or all of the lignin from the oxygenated intermediatestream. The lignin may be passed out of the separation stage as aseparate stream, for example as output stream.

In some embodiments, the oxygenated intermediates can be converted intohigher hydrocarbons through a processing reaction shown schematically asprocessing reaction 136 in FIG. 1. In an embodiment, the processingreaction may comprise a condensation reaction to produce a fuel blend.In an embodiment, the higher hydrocarbons may be part of a fuel blendfor use as a transportation fuel. In such an embodiment, condensation ofthe oxygenated intermediates occurs in the presence of a catalystcapable of forming higher hydrocarbons. While not intending to belimited by theory, it is believed that the production of higherhydrocarbons proceeds through a stepwise addition reaction including theformation of carbon-carbon bond. The resulting reaction products includeany number of compounds, as described in more detail below.

Referring to FIG. 1, in some embodiments, an outlet stream 130containing at least a portion of the oxygenated intermediates can passto a processing reaction or processing reactions. Suitable processingreactions may comprise a variety of catalysts for condensing one or moreoxygenated intermediates to higher hydrocarbons. The higher hydrocarbonsmay comprise a fuel product. The fuel products produced by theprocessing reactions represent the product stream from the overallprocess at higher hydrocarbon stream 150. In an embodiment, the oxygento carbon ratio of the higher hydrocarbons produced through theprocessing reactions is less than 0.5, alternatively less than 0.4, orpreferably less than 0.3.

In one embodiment of the process shown in FIG. 1, the nitrogen andsulfur compounds are removed, and the treated biomass intermediatestream is passed through an APR reaction to form suitable oxygenatedintermediates for the condensation reaction 136. For yet a secondembodiment of the process shown in FIG. 1, the nitrogen and sulfurcompounds are removed, and the treated biomass stream is passed throughan APR reaction to form suitable oxygenated intermediates for thedehydrogenation reaction and alkylation reaction (both represented insystem 136).

The oxygenated intermediates can be processed to produce a fuel blend inone or more processing reactions. In an embodiment, a condensationreaction can be used along with other reactions to generate a fuel blendand may be catalyzed by a catalyst comprising acid or basic functionalsites, or both. In general, without being limited to any particulartheory, it is believed that the basic condensation reactions generallyconsist of a series of steps involving: (1) an optional dehydrogenationreaction; (2) an optional dehydration reaction that may be acidcatalyzed; (3) an aldol condensation reaction; (4) an optionalketonization reaction; (5) an optional furanic ring opening reaction;(6) hydrogenation of the resulting condensation products to form a C4+hydrocarbon; and (7) any combination thereof. Acid catalyzedcondensations may similarly entail optional hydrogenation ordehydrogenation reactions, dehydration, and oligomerization reactions.Additional polishing reactions may also be used to conform the productto a specific fuel standard, including reactions conducted in thepresence of hydrogen and a hydrogenation catalyst to remove functionalgroups from final fuel product. A catalyst comprising a basic functionalsite, both an acid and a basic functional site, and optionallycomprising a metal function, may be used to effect the condensationreaction. In an embodiment, a method of forming a fuel blend from abiomass feedstock may comprise a digester that receives a biomassfeedstock and a digestive solvent operating under conditions toeffectively remove nitrogen and sulfur compounds from said biomassfeedstock and discharges a treated stream comprising a carbohydratehaving less than 35% of the sulfur content and less than 35 wt %nitrogen content based on untreated biomass feedstock on a dry massbasis; an aqueous phase reforming reactor comprising an aqueous phasereforming catalyst that receives the treated stream and discharges anoxygenated intermediate stream, wherein a first portion of theoxygenated intermediate stream is recycled to the digester as at least aportion of the digestive solvent; and a fuels processing reactorcomprising a condensation catalyst that receives a second portion of theoxygenated intermediate stream and discharges a liquid fuel.

In an embodiment, the aldol condensation reaction may be used to producea fuel blend meeting the requirements for a diesel fuel or jet fuel.Traditional diesel fuels are petroleum distillates rich in paraffinichydrocarbons. They have boiling ranges as broad as 187° C. to 417° C.,which are suitable for combustion in a compression ignition engine, suchas a diesel engine vehicle. The American Society of Testing andMaterials (ASTM) establishes the grade of diesel according to theboiling range, along with allowable ranges of other fuel properties,such as cetane number, cloud point, flash point, viscosity, anilinepoint, sulfur content, water content, ash content, copper stripcorrosion, and carbon residue. Thus, any fuel blend meeting ASTM D975can be defined as diesel fuel.

The present invention also provides methods to produce jet fuel. Jetfuel is clear to straw colored. The most common fuel is anunleaded/paraffin oil-based fuel classified as Aeroplane A-1, which isproduced to an internationally standardized set of specifications. Jetfuel is a mixture of a large number of different hydrocarbons, possiblyas many as a thousand or more. The range of their sizes (molecularweights or carbon numbers) is restricted by the requirements for theproduct, for example, freezing point or smoke point. Kerosene-typeAirplane or aviation fuel (including Jet A and Jet A-1) has a carbonnumber distribution between about C8 and C16. Wide-cut or naphtha-typeAirplane fuel (including Jet B) typically has a carbon numberdistribution between about C5 and C15. A fuel blend meeting ASTM D1655can be defined as jet fuel.

In certain embodiments, both aviation fuels (Jet A and Jet B) contain anumber of additives. Useful additives include, but are not limited to,antioxidants, antistatic agents, corrosion inhibitors, and fuel systemicing inhibitor (FSII) agents. Antioxidants prevent gumming and usually,are based on alkylated phenols, for example, AO-30, AO-31, or AO-37.Antistatic agents dissipate static electricity and prevent sparking.Stadis 450 with dinonylnaphthylsulfonic acid (DINNSA) as the activeingredient, is an example. Corrosion inhibitors, e.g., DCI-4A are usedfor civilian and military fuels and DCI-6A is used for military fuels.FSII agents, include, e.g., Di-EGME.

In an embodiment, the oxygenated intermediates may comprise acarbonyl-containing compound that can take part in a base catalyzedcondensation reaction. In some embodiments, an optional dehydrogenationreaction may be used to increase the amount of carbonyl-containingcompounds in the oxygenated intermediate stream to be used as a feed tothe condensation reaction. In these embodiments, the oxygenatedintermediates and/or a portion of the bio-based feedstock stream can bedehydrogenated in the presence of a catalyst.

In an embodiment, a dehydrogenation catalyst may be preferred for anoxygenated intermediate stream comprising alcohols, diols, and triols.In general, alcohols cannot participate in aldol condensation directly.The hydroxyl group or groups present can be converted into carbonyls(e.g., aldehydes, ketones, etc.) in order to participate in an aldolcondensation reaction. A dehydrogenation catalyst may be included toeffect dehydrogenation of any alcohols, diols, or polyols present toform ketones and aldehydes. The dehydration catalyst is typically formedfrom the same metals as used for hydrogenation or aqueous phasereforming, which catalysts are described in more detail above.Dehydrogenation yields are enhanced by the removal or consumption ofhydrogen as it forms during the reaction. The dehydrogenation step maybe carried out as a separate reaction step before an aldol condensationreaction, or the dehydrogenation reaction may be carried out in concertwith the aldol condensation reaction. For concerted dehydrogenation andaldol condensation, the dehydrogenation and aldol condensation functionscan be on the same catalyst. For example, a metalhydrogenation/dehydrogenation functionality may be present on catalystcomprising a basic functionality.

The dehydrogenation reaction may result in the production of acarbonyl-containing compound. Suitable carbonyl-containing compoundsinclude, but are not limited to, any compound comprising a carbonylfunctional group that can form carbanion species or can react in acondensation reaction with a carbanion species, where “carbonyl” isdefined as a carbon atom doubly-bonded to oxygen. In an embodiment, acarbonyl-containing compound can include, but is not limited to,ketones, aldehydes, furfurals, hydroxy carboxylic acids, and, carboxylicacids. The ketones may include, without limitation, hydroxyketones,cyclic ketones, diketones, acetone, propanone, 2-oxopropanal, butanone,butane-2,3-dione, 3-hydroxybutane-2-one, pentanone, cyclopentanone,pentane-2,3-dione, pentane-2,4-dione, hexanone, cyclohexanone,2-methyl-cyclopentanone, heptanone, octanone, nonanone, decanone,undecanone, dodecanone, methylglyoxal, butanedione, pentanedione,diketohexane, dihydroxyacetone, and isomers thereof. The aldehydes mayinclude, without limitation, hydroxyaldehydes, acetaldehyde,glyceraldehyde, propionaldehyde, butyraldehyde, pentanal, hexanal,heptanal, octanal, nonal, decanal, undecanal, dodecanal, and isomersthereof. The carboxylic acids may include, without limitation, formicacid, acetic acid, propionic acid, butanoic acid, pentanoic acid,hexanoic acid, heptanoic acid, isomers and derivatives thereof,including hydroxylated derivatives, such as 2-hydroxybutanoic acid andlactic acid. Furfurals include, without limitation,hydroxylmethylfurfural, 5-hydroxymethyl-2(5H)-furanone,dihydro-5-(hydroxymethyl)-2(3H)-furanone, tetrahydro-2-furoic acid,dihydro-5-(hydroxymethyl)-2(3H)-furanone, tetrahydrofurfuryl alcohol,1-(2-furyl)ethanol, hydroxymethyltetrahydrofurfural, and isomersthereof. In an embodiment, the dehydrogenation reaction results in theproduction of a carbonyl-containing compound that is combined with theoxygenated intermediates to become a part of the oxygenatedintermediates fed to the condensation reaction.

In an embodiment, an acid catalyst may be used to optionally dehydrateat least a portion of the oxygenated intermediate stream. Suitable acidcatalysts for use in the dehydration reaction include, but are notlimited to, mineral acids (e.g., HCl, H₂SO₄), solid acids (e.g.,zeolites, ion-exchange resins) and acid salts (e.g., LaCl₃). Additionalacid catalysts may include, without limitation, zeolites, carbides,nitrides, zirconia, alumina, silica, aluminosilicates, phosphates,titanium oxides, zinc oxides, vanadium oxides, lanthanum oxides, yttriumoxides, scandium oxides, magnesium oxides, cerium oxides, barium oxides,calcium oxides, hydroxides, heteropolyacids, inorganic acids, acidmodified resins, base modified resins, and any combination thereof. Insome embodiments, the dehydration catalyst can also include a modifier.Suitable modifiers include La, Y, Sc, P, B, Bi, Li, Na, K, Rb, Cs, Mg,Ca, Sr, Ba, and any combination thereof. The modifiers may be useful,inter alia, to carry out a concerted hydrogenation/dehydrogenationreaction with the dehydration reaction. In some embodiments, thedehydration catalyst can also include a metal. Suitable metals includeCu, Ag, Au, Pt, Ni, Fe, Co, Ru, Zn, Cd, Ga, In, Rh, Pd, Ir, Re, Mn, Cr,Mo, W, Sn, Os, alloys, and any combination thereof. The dehydrationcatalyst may be self supporting, supported on an inert support or resin,or it may be dissolved in solution.

In some embodiments, the dehydration reaction occurs in the vapor phase.In other embodiments, the dehydration reaction occurs in the liquidphase. For liquid phase dehydration reactions, an aqueous solution maybe used to carry out the reaction. In an embodiment, other solvents inaddition to water, are used to form the aqueous solution. For example,water soluble organic solvents may be present. Suitable solvents caninclude, but are not limited to, hydroxymethylfurfural (HMF),dimethylsulfoxide (DMSO), 1-methyl-n-pyrollidone (NMP), and anycombination thereof. Other suitable aprotic solvents may also be usedalone or in combination with any of these solvents.

In an embodiment, the processing reactions may comprise an optionalketonization reaction. A ketonization reaction may increase the numberof ketone functional groups within at least a portion of the oxygenatedintermediate stream. For example, an alcohol or other hydroxylfunctional group can be converted into a ketone in a ketonizationreaction. Ketonization may be carried out in the presence of a basecatalyst. Any of the base catalysts described above as the basiccomponent of the aldol condensation reaction can be used to effect aketonization reaction. Suitable reaction conditions are known to one ofordinary skill in the art and generally correspond to the reactionconditions listed above with respect to the aldol condensation reaction.The ketonization reaction may be carried out as a separate reactionstep, or it may be carried out in concert with the aldol condensationreaction. The inclusion of a basic functional site on the aldolcondensation catalyst may result in concerted ketonization and aldolcondensation reactions.

In an embodiment, the processing reactions may comprise an optionalfuranic ring opening reaction. A furanic ring opening reaction mayresult in the conversion of at least a portion of any oxygenatedintermediates comprising a furanic ring into compounds that are morereactive in an aldol condensation reaction. A furanic ring openingreaction may be carried out in the presence of an acidic catalyst. Anyof the acid catalysts described above as the acid component of the aldolcondensation reaction can be used to effect a furanic ring openingreaction. Suitable reaction conditions are known to one of ordinaryskill in the art and generally correspond to the reaction conditionslisted above with respect to the aldol condensation reaction. Thefuranic ring opening reaction may be carried out as a separate reactionstep, or it may be carried out in concert with the aldol condensationreaction. The inclusion of an acid functional site on the aldolcondensation catalyst may result in a concerted furanic ring openingreaction and aldol condensation reactions. Such an embodiment may beadvantageous as any furanic rings can be opened in the presence of anacid functionality and reacted in an aldol condensation reaction using abase functionality. Such a concerted reaction scheme may allow for theproduction of a greater amount of higher hydrocarbons to be formed for agiven oxygenated intermediate feed.

In an embodiment, production of a C4+ compound occurs by condensation,which may include aldol-condensation, of the oxygenated intermediates inthe presence of a condensation catalyst. Aldol-condensation generallyinvolves the carbon-carbon coupling between two compounds, at least oneof which may contain a carbonyl group, to form a larger organicmolecule. For example, acetone may react with hydroxymethylfurfural toform a C9 species, which may subsequently react with anotherhydroxymethylfurfural molecule to form a C15 species. The reaction isusually carried out in the presence of a condensation catalyst. Thecondensation reaction may be carried out in the vapor or liquid phase.In an embodiment, the reaction may take place at a temperature in therange of from about 5° C. to about 375° C., depending on the reactivityof the carbonyl group.

The condensation catalyst will generally be a catalyst capable offorming longer chain compounds by linking two molecules through a newcarbon-carbon bond, such as a basic catalyst, a multi-functionalcatalyst having both acid and base functionality, or either type ofcatalyst also comprising an optional metal functionality. In anembodiment, the multi-functional catalyst will be a catalyst having botha strong acid and a strong base functionality. In an embodiment, aldolcatalysts can comprise Li, Na, K, Cs, B, Rb, Mg, Ca, Sr, Si, Ba, Al, Zn,Ce, La, Y, Sc, Y, Zr, Ti, hydrotalcite, zinc-aluminate, phosphate,base-treated aluminosilicate zeolite, a basic resin, basic nitride,alloys or any combination thereof. In an embodiment, the base catalystcan also comprise an oxide of Ti, Zr, V, Nb, Ta, Mo, Cr, W, Mn, Re, Al,Ga, In, Co, Ni, Si, Cu, Zn, Sn, Cd, Mg, P, Fe, or any combinationthereof. In an embodiment, the condensation catalyst comprises amixed-oxide base catalyst. Suitable mixed-oxide base catalysts cancomprise a combination of magnesium, zirconium, and oxygen, which maycomprise, without limitation: Si—Mg—O, Mg—Ti—O, Y—Mg—O, Y—Zr—O, Ti—Zr—O,Ce—Zr—O, Ce—Mg—O, Ca—Zr—O, La—Zr—O, B—Zr—O, La—Ti—O, B—Ti—O, and anycombinations thereof. Different atomic ratios of Mg/Zr or thecombinations of various other elements constituting the mixed oxidecatalyst may be used ranging from about 0.01 to about 50. In anembodiment, the condensation catalyst further includes a metal or alloyscomprising metals, such as Cu, Ag, Au, Pt, Ni, Fe, Co, Ru, Zn, Cd, Ga,In, Rh, Pd, Ir, Re, Mn, Cr, Mo, W, Sn, Bi, Pb, Os, alloys andcombinations thereof. Such metals may be preferred when adehydrogenation reaction is to be carried out in concert with the aldolcondensation reaction. In an embodiment, preferred Group IA materialsinclude Li, Na, K, Cs and Rb. In an embodiment, preferred Group IIAmaterials include Mg, Ca, Sr and Ba. In an embodiment, Group IIBmaterials include Zn and Cd. In an embodiment, Group IIIB materialsinclude Y and La. Basic resins include resins that exhibit basicfunctionality. The base catalyst may be self-supporting or adhered toany one of the supports further described below, including supportscontaining carbon, silica, alumina, zirconia, titania, vanadia, ceria,nitride, boron nitride, heteropolyacids, alloys and mixtures thereof.

In one embodiment, the condensation catalyst is derived from thecombination of MgO and Al₂O₃ to form a hydrotalcite material. Anotherpreferred material contains ZnO and Al₂O₃ in the form of a zincaluminate spinel. Yet another preferred material is a combination ofZnO, Al₂O₃, and CuO. Each of these materials may also contain anadditional metal function provided by a Group VIIIB metal, such as Pd orPt. Such metals may be preferred when a dehydrogenation reaction is tobe carried out in concert with the aldol condensation reaction. In oneembodiment, the base catalyst is a metal oxide containing Cu, Ni, Zn, V,Zr, or mixtures thereof. In another embodiment, the base catalyst is azinc aluminate metal containing Pt, Pd Cu, Ni, or mixtures thereof.

Preferred loading of the primary metal in the condensation catalyst isin the range of 0.10 wt % to 25 wt %, with weight percentages of 0.10%and 0.05% increments between, such as 1.00%, 1.10%, 1.15%, 2.00%, 2.50%,5.00%, 10.00%, 12.50%, 15.00% and 20.00%. The preferred atomic ratio ofthe second metal, if any, is in the range of 0.25-to-1 to 10-to-1,including ratios there between, such as 0.50, 1.00, 2.50, 5.00, and7.50-to-1.

In some embodiments, the base catalyzed condensation reaction isperformed using a condensation catalyst with both an acid and basefunctionality. The acid-aldol condensation catalyst may comprisehydrotalcite, zinc-aluminate, phosphate, Li, Na, K, Cs, B, Rb, Mg, Si,Ca, Sr, Ba, Al, Ce, La, Sc, Y, Zr, Ti, Zn, Cr, or any combinationthereof. In further embodiments, the acid-base catalyst may also includeone or more oxides from the group of Ti, Zr, V, Nb, Ta, Mo, Cr, W, Mn,Re, Al, Ga, In, Fe, Co, Ir, Ni, Si, Cu, Zn, Sn, Cd, P, and combinationsthereof. In an embodiment, the acid-base catalyst includes a metalfunctionality provided by Cu, Ag, Au, Pt, Ni, Fe, Co, Ru, Zn, Cd, Ga,In, Rh, Pd, Ir, Re, Mn, Cr, Mo, W, Sn, Os, alloys or combinationsthereof.

In one embodiment, the catalyst further includes Zn, Cd or phosphate. Inone embodiment, the condensation catalyst is a metal oxide containingPd, Pt, Cu or Ni, and even more preferably an aluminate or zirconiummetal oxide containing Mg and Cu, Pt, Pd or Ni. The acid-base catalystmay also include a hydroxyapatite (HAP) combined with any one or more ofthe above metals. The acid-base catalyst may be self-supporting oradhered to any one of the supports further described below, includingsupports containing carbon, silica, alumina, zirconia, titania, vanadia,ceria, nitride, boron nitride, heteropolyacids, alloys and mixturesthereof.

In an embodiment, the condensation catalyst may also include zeolitesand other microporous supports that contain Group IA compounds, such asLi, NA, K, Cs and Rb. Preferably, the Group IA material is present in anamount less than that required to neutralize the acidic nature of thesupport. A metal function may also be provided by the addition of groupVIIIB metals, or Cu, Ga, In, Zn or Sn. In one embodiment, thecondensation catalyst is derived from the combination of MgO and Al₂O₃to form a hydrotalcite material. Another preferred material contains acombination of MgO and ZrO₂, or a combination of ZnO and Al₂O₃. Each ofthese materials may also contain an additional metal function providedby copper or a Group VIIIB metal, such as Ni, Pd, Pt, or combinations ofthe foregoing.

If a Group IIB, VIIB, VIIB, VIIIB, IIA or IVA metal is included in thecondensation catalyst, the loading of the metal is in the range of 0.10wt % to 10 wt %, with weight percentages of 0.10% and 0.05% incrementsbetween, such as 1.00%, 1.10%, 1.15%, 2.00%, 2.50%, 5.00% and 7.50%,etc. If a second metal is included, the preferred atomic ratio of thesecond metal is in the range of 0.25-to-1 to 5-to-1, including ratiosthere between, such as 0.50, 1.00, 2.50 and 5.00-to-1.

The condensation catalyst may be self-supporting (i.e., the catalystdoes not need another material to serve as a support), or may require aseparate support suitable for suspending the catalyst in the reactantstream. One exemplary support is silica, especially silica having a highsurface area (greater than 100 square meters per gram), obtained bysol-gel synthesis, precipitation, or fuming. In other embodiments,particularly when the condensation catalyst is a powder, the catalystsystem may include a binder to assist in forming the catalyst into adesirable catalyst shape. Applicable forming processes includeextrusion, pelletization, oil dropping, or other known processes. Zincoxide, alumina, and a peptizing agent may also be mixed together andextruded to produce a formed material. After drying, this material iscalcined at a temperature appropriate for formation of the catalyticallyactive phase, which usually requires temperatures in excess of 450° C.Other catalyst supports as known to those of ordinary skill in the artmay also be used.

In some embodiments, a dehydration catalyst, a dehydrogenation catalyst,and the condensation catalyst can be present in the same reactor as thereaction conditions overlap to some degree. In these embodiments, adehydration reaction and/or a dehydrogenation reaction may occursubstantially simultaneously with the condensation reaction. In someembodiments, a catalyst may comprise active sites for a dehydrationreaction and/or a dehydrogenation reaction in addition to a condensationreaction. For example, a catalyst may comprise active metals for adehydration reaction and/or a dehydrogenation reaction along with acondensation reaction at separate sites on the catalyst or as alloys.Suitable active elements can comprise any of those listed above withrespect to the dehydration catalyst, dehydrogenation catalyst, and thecondensation catalyst. Alternately, a physical mixture of dehydration,dehydrogenation, and condensation catalysts could be employed. While notintending to be limited by theory, it is believed that using acondensation catalyst comprising a metal and/or an acid functionalitymay assist in pushing the equilibrium limited aldol condensationreaction towards completion. Advantageously, this can be used to effectmultiple condensation reactions with dehydration and/or dehydrogenationof intermediates, in order to form (via condensation, dehydration,and/or dehydrogenation) higher molecular weight oligomers as desired toproduce jet or diesel fuel.

The specific C4+ compounds produced in the condensation reaction willdepend on various factors, including, without limitation, the type ofoxygenated intermediates in the reactant stream, condensationtemperature, condensation pressure, the reactivity of the catalyst, andthe flow rate of the reactant stream as it affects the space velocity,GHSV and WHSV. Preferably, the reactant stream is contacted with thecondensation catalyst at a WHSV that is appropriate to produce thedesired hydrocarbon products. The WHSV is preferably at least about 0.1grams of oxygenated intermediates in the reactant stream per hour, morepreferably the WHSV is between about 0.1 to 40.0 g/g hr, including aWHSV of about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 20, 25,30, 35 g/g hr, and increments between.

In general, the condensation reaction should be carried out at atemperature at which the thermodynamics of the proposed reaction arefavorable. For condensed phase liquid reactions, the pressure within thereactor must be sufficient to maintain at least a portion of thereactants in the condensed liquid phase at the reactor inlet. For vaporphase reactions, the reaction should be carried out at a temperaturewhere the vapor pressure of the oxygenates is at least about 10 kPa, andthe thermodynamics of the reaction are favorable. The condensationtemperature will vary depending upon the specific oxygenatedintermediates used, but is generally in the range of from about 75° C.to 500° C. for reactions taking place in the vapor phase, and morepreferably from about 125° C. to 450° C. For liquid phase reactions, thecondensation temperature may be from about 5° C. to 475° C., and thecondensation pressure from about 0.1 kPa to 10,000 kPa. Preferably, thecondensation temperature is between about 15° C. and 300° C., or betweenabout 15° C. and 250° C. for difficult substrates.

Varying the factors above, as well as others, will generally result in amodification to the specific composition and yields of the C4+compounds. For example, varying the temperature and/or pressure of thereactor system, or the particular catalyst formulations, may result inthe production of C4+ alcohols and/or ketones instead of C4+hydrocarbons. The C4+ hydrocarbon product may also contain a variety ofolefins, and alkanes of various sizes (typically branched alkanes).Depending upon the condensation catalyst used, the hydrocarbon productmay also include aromatic and cyclic hydrocarbon compounds. The C4+hydrocarbon product may also contain undesirably high levels of olefins,which may lead to coking or deposits in combustion engines, or otherundesirable hydrocarbon products. In such event, the hydrocarbonmolecules produced may be optionally hydrogenated to reduce the ketonesto alcohols and hydrocarbons, while the alcohols and unsaturatedhydrocarbon may be reduced to alkanes, thereby forming a more desirablehydrocarbon product having low levels of olefins, aromatics or alcohols.

The condensation reactions may be carried out in any reactor of suitabledesign, including continuous-flow, batch, semi-batch or multi-systemreactors, without limitation as to design, size, geometry, flow rates,etc. The reactor system may also use a fluidized catalytic bed system, aswing bed system, fixed bed system, a moving bed system, or acombination of the above. In some embodiments, bi-phasic (e.g.,liquid-liquid) and tri-phasic (e.g., liquid-liquid-solid) reactors maybe used to carry out the condensation reactions.

In a continuous flow system, the reactor system can include an optionaldehydrogenation bed adapted to produce dehydrogenated oxygenatedintermediates, an optional dehydration bed adapted to produce dehydratedoxygenated intermediates, and a condensation bed to produce C4+compounds from the oxygenated intermediates. The dehydrogenation bed isconfigured to receive the reactant stream and produce the desiredoxygenated intermediates, which may have an increase in the amount ofcarbonyl-containing compounds. The de-hydration bed is configured toreceive the reactant stream and produce the desired oxygenatedintermediates. The condensation bed is configured to receive theoxygenated intermediates for contact with the condensation catalyst andproduction of the desired C4+ compounds. For systems with one or morefinishing steps, an additional reaction bed for conducting the finishingprocess or processes may be included after the condensation bed.

In an embodiment, the optional dehydration reaction, the optionaldehydrogenation reaction, the optional ketonization reaction, theoptional ring opening reaction, and the condensation reaction catalystbeds may be positioned within the same reactor vessel or in separatereactor vessels in fluid communication with each other. Each reactorvessel preferably includes an outlet adapted to remove the productstream from the reactor vessel. For systems with one or more finishingsteps, the finishing reaction bed or beds may be within the same reactorvessel along with the condensation bed or in a separate reactor vesselin fluid communication with the reactor vessel having the condensationbed.

In an embodiment, the reactor system also includes additional outlets toallow for the removal of portions of the reactant stream to furtheradvance or direct the reaction to the desired reaction products, and toallow for the collection and recycling of reaction byproducts for use inother portions of the system. In an embodiment, the reactor system alsoincludes additional inlets to allow for the introduction of supplementalmaterials to further advance or direct the reaction to the desiredreaction products, and to allow for the recycling of reaction byproductsfor use in other reactions.

In an embodiment, the reactor system also includes elements which allowfor the separation of the reactant stream into different componentswhich may find use in different reaction schemes or to simply promotethe desired reactions. For instance, a separator unit, such as a phaseseparator, extractor, purifier or distillation column, may be installedprior to the condensation step to remove water from the reactant streamfor purposes of advancing the condensation reaction to favor theproduction of higher hydrocarbons. In an embodiment, a separation unitis installed to remove specific intermediates to allow for theproduction of a desired product stream containing hydrocarbons within aparticular carbon number range, or for use as end products or in othersystems or processes.

The condensation reaction can produce a broad range of compounds withcarbon numbers ranging from C4 to C30 or greater. Exemplary compoundsinclude, but are not limited to, C4+ alkanes, C4+ alkenes, C5+cycloalkanes, C5+ cycloalkenes, aryls, fused aryls, C4+ alcohols, C4+ketones, and mixtures thereof. The C4+ alkanes and C4+ alkenes may rangefrom 4 to 30 carbon atoms (C4-C30 alkanes and C4-C30 alkenes) and may bebranched or straight chained alkanes or alkenes. The C4+ alkanes and C4+alkenes may also include fractions of C7-C14, C12-C24 alkanes andalkenes, respectively, with the C7-C14 fraction directed to jet fuelblend, and the C12-C24 fraction directed to a diesel fuel blend andother industrial applications. Examples of various C4+ alkanes and C4+alkenes include, without limitation, butane, butene, pentane, pentene,2-methylbutane, hexane, hexene, 2-methylpentane, 3-methylpentane,2,2-dimethylbutane, 2,3-dimethylbutane, heptane, heptene, octane,octene, 2,2,4,-trimethylpentane, 2,3-dimethyl hexane,2,3,4-trimethylpentane, 2,3-dimethylpentane, nonane, nonene, decane,decene, undecane, undecene, dodecane, dodecene, tridecane, tridecene,tetradecane, tetradecene, pentadecane, pentadecene, hexadecane,hexadecene, heptyldecane, heptyldecene, octyldecane, octyldecene,nonyldecane, nonyldecene, eicosane, eicosene, uneicosane, uneicosene,doeicosane, doeicosene, trieicosane, trieicosene, tetraeicosane,tetraeicosene, and isomers thereof.

The C5+ cycloalkanes and C5+ cycloalkenes have from 5 to 30 carbon atomsand may be unsubstituted, mono-substituted or multi-substituted. In thecase of mono-substituted and multi-substituted compounds, thesubstituted group may include a branched C3+ alkyl, a straight chain C1+alkyl, a branched C3+ alkylene, a straight chain C1+ alkylene, astraight chain C2+ alkylene, a phenyl or a combination thereof. In oneembodiment, at least one of the substituted groups include a branchedC3-C12 alkyl, a straight chain C1-C12 alkyl, a branched C3-C12 alkylene,a straight chain C1-C12 alkylene, a straight chain C2-C12 alkylene, aphenyl or a combination thereof. In yet another embodiment, at least oneof the substituted groups includes a branched C3-C4 alkyl, a straightchain C1-C4 alkyl, a branched C3-C4 alkylene, a straight chain C1-C4alkylene, a straight chain C2-C4 alkylene, a phenyl, or any combinationthereof. Examples of desirable C5+ cycloalkanes and C5+ cycloalkenesinclude, without limitation, cyclopentane, cyclopentene, cyclohexane,cyclohexene, methyl-cyclopentane, methyl-cyclopentene,ethyl-cyclopentane, ethyl-cyclopentene, ethyl-cyclohexane,ethyl-cyclohexene, and isomers thereof.

Aryls will generally consist of an aromatic hydrocarbon in either anunsubstituted (phenyl), mono-substituted or multi-substituted form. Inthe case of mono-substituted and multi-substituted compounds, thesubstituted group may include a branched C3+ alkyl, a straight chain C1+alkyl, a branched C3+ alkylene, a straight chain C2+ alkylene, a phenylor a combination thereof. In one embodiment, at least one of thesubstituted groups includes a branched C3-C12 alkyl, a straight chainC1-C12 alkyl, a branched C3-C12 alkylene, a straight chain C2-C12alkylene, a phenyl, or any combination thereof. In yet anotherembodiment, at least one of the substituted groups includes a branchedC3-C4 alkyl, a straight chain C1-C4 alkyl, a branched C3-C4 alkylene,straight chain C2-C4 alkylene, a phenyl, or any combination thereof.Examples of various aryls include, without limitation, benzene, toluene,xylene (dimethylbenzene), ethyl benzene, para xylene, meta xylene, orthoxylene, C9 aromatics.

Fused aryls will generally consist of bicyclic and polycyclic aromatichydrocarbons, in either an unsubstituted, mono-substituted ormulti-substituted form. In the case of mono-substituted andmulti-substituted compounds, the substituted group may include abranched C3+ alkyl, a straight chain C1+ alkyl, a branched C3+ alkylene,a straight chain C2+ alkylene, a phenyl or a combination thereof. Inanother embodiment, at least one of the substituted groups includes abranched C3-C4 alkyl, a straight chain C1-C4 alkyl, a branched C3-C4alkylene, a straight chain C2-C4 alkylene, a phenyl, or any combinationthereof. Examples of various fused aryls include, without limitation,naphthalene, anthracene, tetrahydronaphthalene, anddecahydronaphthalene, indane, indene, and isomers thereof.

The moderate fractions, such as C7-C14, may be separated for jet fuel,while heavier fractions, (e.g., C12-C24), may be separated for dieseluse. The heaviest fractions may be used as lubricants or cracked toproduce additional gasoline and/or diesel fractions. The C4+ compoundsmay also find use as industrial chemicals, whether as an intermediate oran end product. For example, the aryls toluene, xylene, ethyl benzene,para xylene, meta xylene, ortho xylene may find use as chemicalintermediates for the production of plastics and other products.Meanwhile, the C9 aromatics and fused aryls, such as naphthalene,anthracene, tetrahydronaphthalene, and decahydronaphthalene, may finduse as solvents in industrial processes.

In an embodiment, additional processes are used to treat the fuel blendto remove certain components or further conform the fuel blend to adiesel or jet fuel standard. Suitable techniques include hydrotreatingto reduce the amount of or remove any remaining oxygen, sulfur, ornitrogen in the fuel blend. The conditions for hydrotreating ahydrocarbon stream are known to one of ordinary skill in the art.

In an embodiment, hydrogenation is carried out in place of or after thehydrotreating process to saturate at least some olefinic bonds. In someembodiments, a hydrogenation reaction may be carried out in concert withthe aldol condensation reaction by including a metal functional groupwith the aldol condensation catalyst. Such hydrogenation may beperformed to conform the fuel blend to a specific fuel standard (e.g., adiesel fuel standard or a jet fuel standard). The hydrogenation of thefuel blend stream can be carried out according to known procedures,either with the continuous or batch method. The hydrogenation reactionmay be used to remove a remaining carbonyl group or hydroxyl group. Insuch event, any one of the hydrogenation catalysts described above maybe used. Such catalysts may include any one or more of the followingmetals, Cu, Ni, Fe, Co, Ru, Pd, Rh, Pt, Ir, Os, alloys or combinationsthereof, alone or with promoters such as Au, Ag, Cr, Zn, Mn, Sn, Cu, Bi,and alloys thereof, may be used in various loadings ranging from about0.01 wt % to about 20 wt % on a support as described above. In general,the finishing step is carried out at finishing temperatures of betweenabout 80° C. to 250° C., and finishing pressures in the range of about700 kPa to 15,000 kPa. In one embodiment, the finishing step isconducted in the vapor phase or liquid phase, and uses in situ generatedH2 (e.g., generated in the APR reaction step), external H2, recycled H2,or combinations thereof, as necessary.

In an embodiment, isomerization is used to treat the fuel blend tointroduce a desired degree of branching or other shape selectivity to atleast some components in the fuel blend. It may be useful to remove anyimpurities before the hydrocarbons are contacted with the isomerizationcatalyst. The isomerization step comprises an optional stripping step,wherein the fuel blend from the oligomerization reaction may be purifiedby stripping with water vapor or a suitable gas such as lighthydrocarbon, nitrogen or hydrogen. The optional stripping step iscarried out in a counter-current manner in a unit upstream of theisomerization catalyst, wherein the gas and liquid are contacted witheach other, or before the actual isomerization reactor in a separatestripping unit utilizing counter-current principle.

After the optional stripping step the fuel blend can be passed to areactive isomerization unit comprising one or several catalyst bed(s).The catalyst beds of the isomerization step may operate either inco-current or counter-current manner. In the isomerization step, thepressure may vary from 2000 kPa to 15,000 kPa, preferably in the rangeof 2000 kPa to 10,000 kPa, the temperature being between 200° C. and500° C., preferably between 300° C. and 400° C. In the isomerizationstep, any isomerization catalysts known in the art may be used. Suitableisomerization catalysts can contain molecular sieve and/or a metal fromGroup VII and/or a carrier. In an embodiment, the isomerization catalystcontains SAPO-11 or SAPO41 or ZSM-22 or ZSM-23 or ferrierite and Pt, Pdor Ni and Al2O3 or SiO2. Typical isomerization catalysts are, forexample, Pt/SAPO-11/Al2O3, Pt/ZSM-22/Al2O3, Pt/ZSM-23/Al2O3 andPt/SAPO-11/SiO2.

Other factors, such as the concentration of water or undesiredoxygenated intermediates, may also effect the composition and yields ofthe C4+ compounds, as well as the activity and stability of thecondensation catalyst. In such event, the process may include adewatering step that removes a portion of the water prior to thecondensation reaction and/or the optional dehydration reaction, or aseparation unit for removal of the undesired oxygenated intermediates.For instance, a separator unit, such as a phase separator, extractor,purifier or distillation column, may be installed prior to thecondensation step so as to remove a portion of the water from thereactant stream containing the oxygenated intermediates. A separationunit may also be installed to remove specific oxygenated intermediatesto allow for the production of a desired product stream containinghydrocarbons within a particular carbon range, or for use as endproducts or in other systems or processes.

Thus, in one embodiment, the fuel blend produced by the processesdescribed herein is a hydrocarbon mixture that meets the requirementsfor jet fuel (e.g., conforms with ASTM D1655). In another embodiment,the product of the processes described herein is a hydrocarbon mixturethat comprises a fuel blend meeting the requirements for a diesel fuel(e.g., conforms with ASTM D975).

Yet in another embodiment of the invention, the C2+ olefins are producedby catalytically reacting the oxygenated intermediates in the presenceof a dehydration catalyst at a dehydration temperature and dehydrationpressure to produce a reaction stream comprising the C2+ olefins. TheC2+ olefins comprise straight or branched hydrocarbons containing one ormore carbon-carbon double bonds. In general, the C2+ olefins containfrom 2 to 8 carbon atoms, and more preferably from 3 to 5 carbon atoms.In one embodiment, the olefins comprise propylene, butylene, pentylene,isomers of the foregoing, and mixtures of any two or more of theforegoing. In another embodiment, the C2+ olefins include C4+ olefinsproduced by catalytically reacting a portion of the C2+ olefins over anolefin isomerization catalyst. In an embodiment, a method of forming afuel blend from a biomass feedstock may comprise a digester thatreceives a biomass feedstock and a digestive solvent operating underconditions to effectively remove nitrogen and sulfur compounds from saidbiomass feedstock and discharges a treated stream comprising acarbohydrate having less than 35% of the sulfur content and less than35% of the nitrogen content based on the untreated biomass feedstock ona dry mass basis; an aqueous phase reforming reactor comprising anaqueous phase reforming catalyst that receives the treated stream anddischarges an oxygenated intermediate, wherein a first portion of theoxygenated intermediate stream is recycled to the digester as at least aportion of the digestive solvent; a first fuels processing reactorcomprising a dehydrogenation catalyst that receives a second portion ofthe oxygenated intermediate stream and discharges an olefin-containingstream; and a second fuels processing reactor comprising an alkylationcatalyst that receives the olefin-containing stream and discharges aliquid fuel.

The dehydration catalyst comprises a member selected from the groupconsisting of an acidic alumina, aluminum phosphate, silica-aluminaphosphate, amorphous silica-alumina, aluminosilicate, zirconia, sulfatedzirconia, tungstated zirconia, tungsten carbide, molybdenum carbide,titania, sulfated carbon, phosphated carbon, phosphated silica,phosphated alumina, acidic resin, heteropolyacid, inorganic acid, and acombination of any two or more of the foregoing. In one embodiment, thedehydration catalyst further comprises a modifier selected from thegroup consisting of Ce, Y, Sc, La, Li, Na, K, Rb, Cs, Mg, Ca, Sr, Ba, P,B, Bi, and a combination of any two or more of the foregoing. In anotherembodiment, the dehydration catalyst further comprises an oxide of anelement, the element selected from the group consisting of Ti, Zr, V,Nb, Ta, Mo, Cr, W, Mn, Re, Al, Ga, In, Fe, Co, Ir, Ni, Si, Cu, Zn, Sn,Cd, P, and a combination of any two or more of the foregoing. In yetanother embodiment, the dehydration catalyst further comprises a metalselected from the group consisting of Cu, Ag, Au, Pt, Ni, Fe, Co, Ru,Zn, Cd, Ga, In, Rh, Pd, Ir, Re, Mn, Cr, Mo, W, Sn, Os, an alloy of anytwo or more of the foregoing, and a combination of any two or more ofthe foregoing.

In yet another embodiment, the dehydration catalyst comprises analuminosilicate zeolite. In one version, the dehydration catalystfurther comprises a modifier selected from the group consisting of Ga,In, Zn, Fe, Mo, Ag, Au, Ni, P, Sc, Y, Ta, a lanthanide, and acombination of any two or more of the foregoing. In another version, thedehydration catalyst further comprises a metal selected from the groupconsisting of Cu, Ag, Au, Pt, Ni, Fe, Co, Ru, Zn, Cd, Ga, In, Rh, Pd,Ir, Re, Mn, Cr, Mo, W, Sn, Os, an alloy of any two or more of theforegoing, and a combination of any two or more of the foregoing.

In another embodiment, the dehydration catalyst comprises a bifunctionalpentasil ring-containing aluminosilicate zeolite. In one version, thedehydration catalyst further comprises a modifier selected from thegroup consisting of Ga, In, Zn, Fe, Mo, Ag, Au, Ni, P, Sc, Y, Ta, alanthanide, and a combination of any two or more of the foregoing. Inanother version, the dehydration catalyst further comprises a metalselected from the group consisting of Cu, Ag, Au, Pt, Ni, Fe, Co, Ru,Zn, Cd, Ga, In, Rh, Pd, Ir, Re, Mn, Cr, Mo, W, Sn, Os, an alloy of anytwo or more of the foregoing, and a combination of any two or more ofthe foregoing.

The dehydration reaction is conducted at a temperature and pressurewhere the thermodynamics are favorable. In general, the reaction may beperformed in the vapor phase, liquid phase, or a combination of both. Inone embodiment, the dehydration temperature is in the range of about100° C. to 500° C., and the dehydration pressure is in the range ofabout 0 kPa to 6500 kPa. In another embodiment, the dehydrationtemperature is in the range of about 125° C. to 450° C., and thedehydration pressure is at least 15 kPa. In another version, thedehydration temperature is in the range of about 150° C. to 350° C., andthe dehydration pressure is in the range of about 750 kPa to 6000 kPa.In yet another version, the dehydration temperature is in the range ofabout 175° C. to 325° C.

The C6+ paraffins are produced by catalytically reacting the C2+ olefinswith a stream of C4+ isoparaffins in the presence of an alkylationcatalyst at an alkylation temperature and alkylation pressure to producea product stream comprising C6+ paraffins. The C4+ isoparaffins includealkanes and cycloalkanes having 4 to 7 carbon atoms, such as isobutane,isopentane, naphthenes, and higher homologues having a tertiary carbonatom (e.g., 2-methylbutane and 2,4-dimethylpentane), isomers of theforegoing, and mixtures of any two or more of the foregoing. In oneembodiment, the stream of C4+ isoparaffins comprises of internallygenerated C4+ isoparaffins, external C4+ isoparaffins, recycled C4+isoparaffins, or combinations of any two or more of the foregoing.

The C6+ paraffins will generally be branched paraffins, but may alsoinclude normal paraffins. In one version, the C6+ paraffins comprises amember selected from the group consisting of a branched C6-10 alkane, abranched C6 alkane, a branched C7 alkane, a branched C8 alkane, abranched C9 alkane, a branched C10 alkane, or a mixture of any two ormore of the foregoing. In one version, the C.sub.6+ paraffins comprisedimethylbutane, 2,2-dimethylbutane, 2,3-dimethylbutane, methylpentane,2-methylpentane, 3-methylpentane, dimethylpentane, 2,3-dimethylpentane,2,4-dimethylpentane, methylhexane, 2,3-dimethylhexane,2,3,4-trimethylpentane, 2,2,4-trimethylpentane, 2,2,3-trimethylpentane,2,3,3-trimethylpentane, dimethylhexane, or mixtures of any two or moreof the foregoing.

The alkylation catalyst comprises a member selected from the group ofsulfuric acid, hydrofluoric acid, aluminum chloride, boron trifluoride,solid phosphoric acid, chlorided alumina, acidic alumina, aluminumphosphate, silica-alumina phosphate, amorphous silica-alumina,aluminosilicate, aluminosilicate zeolite, zirconia, sulfated zirconia,tungstated zirconia, tungsten carbide, molybdenum carbide, titania,sulfated carbon, phosphated carbon, phosphated silica, phosphatedalumina, acidic resin, heteropolyacid, inorganic acid, and a combinationof any two or more of the foregoing. The alkylation catalyst may alsoinclude a mixture of a mineral acid with a Friedel-Crafts metal halide,such as aluminum bromide, and other proton donors.

In one embodiment, the alkylation catalyst comprises an aluminosilicatezeolite. In one version, the alkylation catalyst further comprises amodifier selected from the group consisting of Ga, In, Zn, Fe, Mo, Ag,Au, Ni, P, Sc, Y, Ta, a lanthanide, and a combination of any two or moreof the foregoing. In another version, the alkylation catalyst furthercomprises a metal selected from the group consisting of Cu, Ag, Au, Pt,Ni, Fe, Co, Ru, Zn, Cd, Ga, In, Rh, Pd, Ir, Re, Mn, Cr, Mo, W, Sn, Os,an alloy of any two or more of the foregoing, and a combination of anytwo or more of the foregoing.

In another embodiment, the alkylation catalyst comprises a bifunctionalpentasil ring-containing aluminosilicate zeolite. In one version, thealkylation catalyst further comprises a modifier selected from the groupconsisting of Ga, In, Zn, Fe, Mo, Ag, Au, Ni, P, Sc, Y, Ta, alanthanide, and a combination of any two or more of the foregoing. Inanother version, the alkylation catalyst further comprises a metalselected from the group consisting of Cu, Ag, Au, Pt, Ni, Fe, Co, Ru,Zn, Cd, Ga, In, Rh, Pd, Ir, Re, Mn, Cr, Mo, W, Sn, Os, an alloy of anytwo or more of the foregoing, and a combination of any two or more ofthe foregoing. In one version, the dehydration catalyst and thealkylation catalyst are atomically identical.

The alkylation reaction is conducted at a temperature where thethermodynamics are favorable. In general, the alkylation temperature isin the range of about −20° C. to 300° C., and the alkylation pressure isin the range of about 0 kPa to 8000 kPa. In one version, the alkylationtemperature is in the range of about 100° C. to 300° C. In anotherversion, the alkylation temperature is in the range of about 0° C. to100° C., and the alkylation pressure is at least 750 kPa. In yet anotherversion, the alkylation temperature is in the range of about 0° C. to50° C. and the alkylation pressure is less than 2500 kPa. In still yetanother version, the alkylation temperature is in the range of about 70°C. to 250° C., and the alkylation pressure is in the range of about 750kPa to 8000 kPa. In one embodiment, the alkylation catalyst comprises amineral acid or a strong acid and the alkylation temperature is lessthan 100° C. In another embodiment, the alkylation catalyst comprises azeolite and the alkylation temperature is greater than 100° C.

Another aspect of the present invention is that the C4+ isoparaffins maybe generated internally by catalytically reacting an isoparaffinfeedstock stream comprising C4+ normal paraffins, aromatics and/ornaphthenes in the presence of an isomerization catalyst at anisomerization temperature and isomerization pressure to produceinternally generated C4+ isoparaffins. The C4+ normal paraffins willgenerally include alkanes having 4 to 7 carbon atoms, such as n-butane,n-pentane, n-hexane, n-heptane, and mixtures of any two or more of theforegoing. In one arrangement, the isoparaffin feedstock stream iscollected upstream of the alkylation catalyst from the reaction streamhaving the oxygenated intermediates or the reaction stream having theC2+ olefins and processed for the production of the internally generatedC4+ isoparaffins. In another arrangement, the C4+ normal paraffins,aromatics and/or naphthenes are collected downstream of the alkylationcatalyst from the product stream having the C6+ paraffins and thenrecycled for use in the production of the internally generated C4+isoparaffins. The C4+ isoparaffins may also be provided solely from anexternal source or used to supplement the internally generated C4+isoparaffins. In another version, the C4+ isoparaffins are recycled C4+isoparaffins collected from the product stream having the C6+ paraffins.

The isomerization catalyst is a catalyst capable of reacting a C4+normal paraffin, aromatic or naphthene to produce a C4+ isoparaffin. Inone version, the isomerization catalyst includes a zeolite, zirconia,sulfated zirconia, tung stated zirconia, alumina, silica-alumina, zincaluminate, chlorided alumina, phosphoric acid, or mixtures of any two ormore of the foregoing. In another version, the isomerization catalyst isan acidic beta, mordenite, or ZSM-5 zeolite. In yet another version, theisomerization catalyst further comprises a metal selected from the groupconsisting of Y, Pt, Ru, Ad, Ni, Rh, Ir, Fe, Co, Os, Zn, a lanthanide,or an alloy or combination of any two or more of the foregoing. In stillyet another version, the isomerization catalyst comprises a support, thesupport comprising alumina, sulfated oxide, clay, silica gel, aluminumphosphate, bentonite, kaolin, magnesium silicate, magnesium carbonate,magnesium oxide, aluminum oxide, activated alumina, bauxite, silica,silica-alumina, activated carbon, pumice, zirconia, titania, zirconium,titanium, kieselguhr, or zeolites.

In an embodiment of the present invention, the fuel yield of the currentprocess may be greater than other bio-based feedstock conversionprocesses. Without wishing to be limited by theory, it is believed thatsubstantially removing nitrogen compounds and sulfur compounds from thebiomass prior to the direct APR allows for a greater percentage of thebiomass to be converted into higher hydrocarbons while limiting theformation of degradation products.

To facilitate a better understanding of the present invention, thefollowing examples of certain aspects of some embodiments are given. Inno way should the following examples be read to limit, or define, theentire scope of the invention.

EXAMPLES

Catalyst poisoning, biomass extraction, pretreatment, digestion andreaction studies were conducted in a Parr5000 Hastelloy multireactorcomprising 6×75-milliliter reactors operated in parallel at pressures upto 14,000 kPa, and temperatures up to 275° C., stirred by magnetic stirbar. Alternate studies were conducted in 100-ml Parr4750 reactors, withmixing by top-driven stir shaft impeller, also capable of 14,000 kPa and275° C. Larger scale extraction, pretreatment and digestion tests wereconducted in a 1-Liter Parr reactor with annular basket housing biomassfeed, or with filtered dip tube for direct contacting of biomassslurries.

Reaction samples were analyzed for sugar, polyol, and organic acidsusing an HPLC method entailing a Bio-Rad Aminex HPX-87H column (300mm×7.8 mm) operated at 0.6 ml/minute of a mobile phase of 5 mM sulfuricacid in water, at an oven temperature of 30° C., a run time of 70minutes, and both RI and UV (320 nm) detectors.

Product formation (mono-oxygenates, diols, alkanes, acids) weremonitored via a gas chromatographic (GC) method “DB5-ox”, entailing a60-m×0.32 mm ID DB-5 column of 1 um thickness, with 50:1 split ratio, 2ml/min helium flow, and column oven at 40° C. for 8 minutes, followed byramp to 285° C. at 10° C./min, and a hold time of 53.5 minutes. Injectortemperature was set at 250° C., and detector temperature at 300° C.

Gasoline production potential by condensation reaction was assessed viainjection of one microliter of liquid intermediate product into acatalytic pulse microreactor entailing a GC insert packed with 0.12grams of ZSM-5 catalyst, held at 375° C., followed by Restek Rtx-1701(60-m) and DB-5 (60-m) capillary GC columns in series (120-m totallength, 0.32 mm ID, 0.25 um film thickness) for an Agilent/HP 6890 GCequipped with flame ionization detector. Helium flow was 2.0 ml/min(constant flow mode), with a 10:1 split ratio. Oven temperature was heldat 35° C. for 10 minutes, followed by a ramp to 270° C. at 3° C./min,followed by a 1.67 minute hold time. Detector temperature was 300° C.

Example 1 Catalyst Poisoning by N,S Amino Acid

Two Parr5000 reactors were charged with 20 grams of a mixture of 50%glycerol in deionized water, and 0.35 grams of 1.9% Pt—Re/zirconiacatalyst reduced at 400° C. under hydrogen. Glycerol is one of theintermediates derived from monosaccharides or sugar alcohols in theaqueous phase reforming reaction sequence, and can react via APR to formhydrogen and CO2, as well as monooxygenate intermediates such as acetoneand 2-propanol. It therefore represents a model component for the studyof the APR reaction.

0.03 grams of the N,S amino acid cysteine were added to reactor B, butnot to A. Reactors were pressured with 3500 kPa of H2, and heated to255° C. for 6.5 hours under conditions corresponding to aqueous phasereforming reaction (APR) with pre-addition of a fraction of the hydrogenrequired for reaction, before cooling for GC analysis of products.Results indicated 84.7% conversion of glycerol to mono oxygenate andother expected products for reactor A, but only 57.6% conversion forreactor B. Calculated first order rate constants, per weight fraction ofcatalyst, were 16.5/h/wt-cat for A, vs. 7.5/h/wt-cat for B. The additionof 1500 ppm cysteine was observed to decrease the apparent activity forconversion of glycerol via APR, by a factor of more then two.

A third reaction C was conducted under identical conditions, except with1500 ppm alanine (N-only amino acid), and exhibited an apparent rateconstant of 14/h/wt-cat, or an approximate 12% reduction in activity.

These results indicate substantial poisoning by cysteine (N,S-aminoacid), and moderate poisoning by alanine (N-only amino acid), for theRe-promoted Pt catalyst which can be employed in aqueous phase reforming(APR).

Example 2 Poisoning of Pt/Alumina Catalyst by N,S and N-Only Amino Acid

The experiment of Example 1 was repeated with 5% Pt/alumina catalystEscat 2941 (Strem Chemicals). In addition to reactors A (no amino acid)and B (1500 ppm cysteine), a third reactor C was charged with 1500 ppmof alanine, a N-only amino acid. Measured conversions were 56.7%, 42.3%,and 45.4% for reactors A through C, corresponding to apparent firstorder rate constants of 10.2, 3.0, and 3.2/h/wt-cat. Addition of 1500ppm of either N,S or N-only amino acid was observed to decrease glycerolAPR reaction rates by more than a factor of 3, for the unpromotedPt/alumina catalyst.

Example 3 Poisoning of Ru Catalyst Under APR Conditions

Examples 1A and B were repeated with 5% Ru/C Escat 4401 catalyst (StremChemicals, 50% wet), with an initial charge of 6000 kPa H₂. Conversionfor reactor A (no amino acid) was 56.5%, while conversion for reactor B(1500 ppm cysteine) was only 9%. Apparent first order rate constant forB (1500 ppm cysteine) was only 1.7/h/wt-cat, vs. a rate constant ofreactor A of 14.7/h/wt-cat. This result indicates poisoning by aminoacid of a Ru-based catalyst, in testing conducted under aqueous phasereforming (APR) conditions with pre-addition of a fraction of therequired hydrogen needed for reaction.

Example 4 Poisoning of APR Catalyst Under N2 and H2

For examples 4A and 4B, the experiment of Example 1 was repeated with 5%Pt/alumina catalyst Escat 2941 (Strem Chemicals), but with 3000 kPa N2instead of H2 as the initial gas, such that all required hydrogen mustbe generated by the aqueous phase reforming reaction. Reactor A (noamino acid) exhibited an apparent first-order rate of 18.6/h/wt-cat,while B (1500 ppm cysteine) was severely poisoned with a rate ofglycerol conversion of only 0.9/h/wt-catalyst. These results indicatesubstantial poisoning by cysteine (N,S-amino acid) for the unpromoted Ptcatalyst employed in aqueous phase reforming (APR), conducted underconditions where all H2 was generated in situ via the aqueous phasereforming reaction.

For examples 4C through 4E, the experiment of Example 1 was repeatedwith a Re-modified 1.9% Pt/zirconia catalyst calcined at 400° C. afterimpregnation, and then reduced at 400° C. under hydrogen. The reactionwas conducted with an initial pressure of 5000 kPa H2. Reactor C (nopoison) indicated a first-order rate constant of 53.9/h/wt-cat, whileReactor D with 1500 ppm cysteine (N,S amino acid) gave lower conversionscorresponding to a rate of only 4.8/h/wt-cat. Reactor E with 1500 ppmalanine (N-only amino acid) showed moderate activity, corresponding to arate of 20.2/h/wt-catalyst. This experiment shows substantial poisoningby N,S amino acid cysteine, and moderate poisoning by N-only amino acidalanine, for aqueous phase reforming experiments conducted with glycerolas feed and with pre-addition of a fraction of the required hydrogen atthe start of reaction.

Example 5 N,S- and N Poisoning of Pt/C Catalyst Used for Sorbitol APR

An experiment was conducted in the Parr5000 multireactor using 0.5 gramsof 5% Pt/C as catalyst (50% wet), and 40 grams of 50% sorbitol as feed,for 3 hours at 250° C., with an initial gas feed of 3500 kPa H₂. Finalliquids were analyzed for remaining unconverted sorbitol content by HPLCanalysis. Conversion of reactor A (no amino acid) corresponded to anapparent first order rate constant of 28.8/h/wt-cat, while reactor B(3000 ppm cysteine) exhibited an apparent rate of only 2.8/h/wt-cat.Reactor C (2250 ppm alanine) exhibited an apparent first order rateconstant for sorbitol conversion of 6.0/h/wt-cat. These results indicatepoisoning of sorbitol aqueous phase reforming reaction by cysteine andalanine despite pre-addition of a fraction of the hydrogen required forreaction.

Example 6 Extraction of Biomass

For Example 6, Parr5000 reactors A-C were loaded with 2.1 grams ofsoftwood (pine) chips, comprising 2 whole chips of approximate1-inch×1-inch×3 mm size, trimmed to fit the reactor body, and 20 gramsof a solvent mixture of 25% by weight acetone, 25% isopropanol, and 2%acetic acid in deionized water, designated as “A”-solvent. Reactors D-Fwere loaded with the same amount of pine chips, and deionized wateronly. The reactors were heated overnight under nitrogen, at temperaturesof 170, 190, and 210° C. for reactors A, B, and C, respectively, and forreactors D, E. F, respectively (Table 1).

Partially digested whole chips were carefully removed to Petri dish forvacuum drying overnight at 90° C. to assess undigested dry solids. Finesolids were washed into a filter funnel with Whatman GF/F filter paper,which was also vacuum dried overnight at 90° C. to assess the residualfines solids which precipitated after cooling of the reactors to ambienttemperature. Mass loss from the whole chips was recorded as percentdigested at the extraction temperature. This amount was corrected by themass of fines redeposited upon cool down to 25° C., and recorded as the“% dissolved at 25 C”.

Samples of liquid were analyzed for nitrogen by elemental X-rayanalysis.

TABLE 1 Extraction and Pre-treatment by solvent leaching Liquid/ Nleached T deg dry Chips Dissolved % ppm-dry Sx solvent C. wd % digest@25° C. wood A A-solv 170 11.896 38.4% 34.1% 416 B A-solv 190 11.92552.4% 45.9% 405 C A-solv 210 12.138 100.0% 66.5% 449 D DIWater 17011.930 29.0% 24.2% 143 E DIWater 190 12.756 33.7% 27.5% 268 F DIWater210 11.106 61.6% 45.7% n.a.

As shown in Table 1 extraction and dissolution of biomass was enhancedby the use of water-soluble oxygenated organic solvent in deionizedwater over deionized water. The extent of extraction and digestion wasalso increased by an increase in temperature, with complete digestion ofwood chips at 210° C. in A-solvent. Solvent also increased theextraction of nitrogen, presumed from proteins and amino acids in thewood matrix, where nitrogen observed in the liquid extract is expressedrelative to the mass of dry wood extracted. Sulfur analyses were low, atdetection limits for these samples.

This example demonstrates the use of oxygenated solvent, selected fromcomponents produced in situ via APR of bio-based feed materials inwater, to facilitate extraction and pretreatment of a biomass sample,including N-containing components attributed to the presence of aminoacids and proteins.

Example 7 Biomass Extraction and Reprecipitation in Water and OxygenatedSolvents

A series of experiments were conducted in a 100-ml Parr reactor fittedwith 0.5 micron stainless steel filtered dip tube. Extraction ofsouthern hardwood was examined, with removal of samples via filtered viadip tube at 210° C. temperature (17 hours), to compare the %precipitated solids in the sample after cooling to ambient temperature(nominal 25° C.), with the % solids in the final mixture recovered fromthe reactor as determined via cold filtration. The fraction of biomassextracted and digested was also assessed, by GC analysis of theintermediates formed. In addition to testing of “A-solvent” anddeionized water, 50% ethanol in water, and “B-solvent” entailing 20 wt %ethylene glycol, 20% wt % 1,2-propylene glycol, and 2% acetic acid indeionized water, were also examined. “B-solvent” represents diolintermediates formed in the APR reaction. Assessment of the percentdigestion of initial dry wood was again made by recovering theundigested solids by filtration on Whatman GF/F filter paper, and dryingovernight in a vacuum oven at 90° C.

Results (Table 2) show all solvents can digest a portion of the woodsample at 210° C. A-solvent (25% acetone, 25% isopropanol, and 2% aceticacid) gave the best digestion, or dissolution of biomass. Addition ofoxygenate solvent including those components formed in an APR reactionof bio-based feeds, was observed to improve the retention of dissolvedbiomass components in solution upon cooling to ambient temperature.Presence of lignin in precipitating samples was confirmed by UV-visanalysis in the region of 190-400 nm. While water-only solvent gave goodextraction results at the 210° C. extraction temperature, a substantialportion precipitated upon cooling to 25° C.

TABLE 2 Extraction and re-precipitation of biomass initial 25° C. 210°C. Solvent wood % digest % digest A A-Solvent 5.43% 72.19% 73.84% BB-Solvent 5.80% 41.57% 28.92% C 50% EtOH 5.42% 54.24% 42.32% D DI water5.32% 29.10% 69.33%

Example 8 Short Contact Time Pretreatment and Extraction

For Example 8A, 42.25-grams of an A-solvent mixture (25% acetone, 25%isopropanol, 2% acetic acid) were contacted with 4.308 grams of southernhardwood for 5 hours at 170° C., followed by cooling to room temperaturefor recovery of undigested solids by filtration (Whatman GF/F).Separated liquor was black, indicating removal of color bodies. Therecovered solid pulp was water washed to remove residual solvent. Aportion was dried overnight in a vacuum oven at 90° C., to assess drysolids content of the recovered pulp. Results indicate extraction of47.5% of the original softwood, on a dry mass basis, using a contacttime of 5 hours. X-ray analysis indicated removal of 860 ppm nitrogenbasis the mass of dry wood charged, using the extractive solventpretreatment. Sulfur was below detection in this sample.

In example 8B, extraction and pretreatment were examined with series ofconsecutive experiments conducted with 22.4 grams of softwood (pine) and500-grams deionized water in the 1-Liter stirred reactor with filtereddip tube, and sampling for total organic carbon (TOC) analysis versustime. The leaching studies were conducted overnight at 170, 190, and210° C. A maximum in the TOC content was obtained after only 2 hours at170° C., where 73% of the final leached carbon was obtained. Furtherincrease to 210° C. before removal of liquid by hot filtration, resultedin 65% digestion of the initially charged biomass, as determined byfiltration (Whatman GF/F) of solids remaining in the reactor aftercooling.

These results indicate an ability to pretreat and extract biomasssamples with water and with oxygenated organic solvents in water, with acontact time as low as 2-5 hours. Up to 65% of the nitrogen present inthe biomass was also extracted in a single stage of extraction,providing a pretreated biomass that can be used in subsequent aqueousphase reforming reactions to form liquid fuels.

Example 9 APR Reaction with Pretreated Biomass Pulp

For Example 9, 2.639 grams of wet pulp from Example 8A were added, alongwith 20.2 grams of deionized water, 0.45 grams of 5% Pt/alumina Escat2941 catalyst (Strem Chemicals), and 6000 kPa N2, to a Parr5000 reactor.The reactor was heated with a temperature profile from 170-240° C. over5 hours, followed by isothermal reaction at 240° C. to comprise an18-hour total reaction cycle.

Filtration recovery and overnight vacuum dry of residual solidsindicated 39.5% digestion of the treated pulp. Analysis for productformation by the DB5-ox method indicated 13.4% yield of products, whileinjection of final supernatant into the ZSM-5 pulse microreactordemonstration production of benzene, toluene, xylenes, methyl benzenes,and naphthalenes at a yield corresponding to 20.4% of the original massof dry pulp charged. This result indicates the feasibility of forminggasoline via APR reactive digestion of a solvent-treated hardwood pulp.

Example 10 APR of Aqueous Digestive Solvent-Pretreated Biomass Pulp

A sample of mixed hardwoods pulp was obtained from an organic solvent(ethanol-water) extract step. An APR reaction was conducted in a theParr100 reactor using 5% Pt/alumina Escat 2941 as catalyst in APR modeunder 3500 kPa of N2, and a heating schedule of 2.5 hours at 170° C.,followed by 2.5 hours at 210° C., followed by overnight (20.25 hourstotal) at 250° C.

Following reaction, solids were recovered by filtration on Whatman #2filter paper, and oven dried overnight at 90° C. to assess recovery. 85%of the pulp was digested. Acetic acid formation was evident at 0.10 wt %(GC). Final pH of 3.14 was observed, despite no acid addition to feed.Total estimated GC wt % via the DB-5ox method matched or exceeded thatcalculated from the mass of pulp digested, indicating high selectivityto desired monooxygenates intermediates. ZSM-5 pulse microreactorindicated formation of alkanes, benzene, toluene, xylenes,trimethlybenzenes, and naphthalenes, at yields in excess of 30% of theoriginal pulp fed.

This example demonstrates the in situ formation of organic acids whichcan aid in the reaction and digestion of biomass samples to formintermediates which can be further reacted to liquid fuels.

Example 11 Hydrogenolysis and APR of an Digestive Solvent-PretreatedBiomass Pulp

5.14 grams of southern hardwood were treated with 50.3 grams ofA-solvent in a Parr5000 reactor under 3500 kPa N2 using a temperatureramp of 150° C.-170° C. over 1 hour, followed by 4 hours at 170° C. Adark brown liquor was obtained, indicating extraction of color bodiesand other extractables. pH of the recovered liquid was 2.9. Undigestedsolids were recovered by filtration on Whatman GF/F filter paper, and asolid pulp sample was dried overnight in a vacuum oven at 90° C. toassess recovery. 48.8% of the initially charged hardwood was extracted,leaving a light brown solid pulp.

3.0 grams of the wet pulp were charged to a Parr5000 reactor, with0.35-grams of a Re-promoted 1.9% Pt/zirconia catalyst. H2 was added at5000 kPa, before ramping in temperature from 170 to 210° C. over 3hours, followed by 15 hours at 210° C. to complete reaction. GC analysisby the DB5-ox method indicated 96% yield of polyols and mono-oxygenateswith retention time less than sorbitol. Final reaction product wascycled to yet another Parr5000 reactor charged with the sameRe—Pt/zirconia catalyst, to effect aqueous phase reforming at 240° C.

This examples demonstrates that the combination of biomass pretreatmentwith an oxygenated organic solvent mixture in water, followed byreaction of the pretreated biomass pulp with an APR catalyst in thepresence of a portion of the hydrogen required for reaction at a firstreaction temperature of 170-210° C., produces a high yield of diols andmono-oxygenates. The diol and mono-oxygenate intermediate product can befurther converted to mono-oxygenates and additional hydrogen by anadditional reaction at a second, higher temperature (240° C.).

Example 12 APR of Alkali Pretreated Biomass Pulp

22.4 grams of softwood (pine) were contacted with 500-grams of deionizedwater in a 1-liter stirred reactor, with overnight heating at 210° C.Filtration and recovery of solids indicated 65.1% digestion to form aliquid extract at pH 3.7.

4.484 grams of the water-extracted solids were contacted with 25.03grams of 1N NaOH at 155° C. for 2 hours, to simulate alkali (Kraft)pulping. A black liquid extract was obtained. The residual solids werewater washed to remove residual base. 3.51 grams of the washed, treatedpulp solids were added with 20.194 grams of an aqueous solvent, alongwith 0.454 grams of 5% Pt/alumina Escat 2941 catalyst (Strem Chemicals),and 4800 kPa of nitrogen. Temperature was ramped from 170-240° C. over 5hours, followed by isothermal reaction at 240° C. to complete an 18 hourcycle.

Final pH of the reaction mixture was 6.73, indicating water wash wasonly partially effective in removing alkali base. Digestion of the pulpwas only 11%, and injection of final liquid into the ZSM-5 pulsemicroreactor gave an estimated conversion to alkanes, benzene, toluene,xylenes, trimethlybenzenes, and naphthalenes of only about 6%, relativeto the mass of biomass pulp charged to the initial reaction step. Theseresults indicate that failure to remove residual alkali base viaeffective water washing following alkaili pulping of softwood, canresult in low yields for a subsequent hydrogenolysis and APR conversionreaction.

What is claimed is:
 1. A method comprising: (i) providing a biomasscontaining celluloses, hemicelluloses, lignin, nitrogen, and sulfurcompounds; (ii) removing sulfur compounds and nitrogen compounds fromsaid biomass by contacting the biomass with a digestive solvent to forma pretreated biomass containing soluble carbohydrates and having lessthan 35% of the sulfur content and less than 35% of the nitrogen contentbased on untreated biomass on a dry mass basis; (iii) contacting thepretreated biomass with an aqueous phase reforming catalyst to form aplurality of oxygenated intermediates; and (vi) processing at least aportion of the oxygenated intermediates to form a liquid fuel.
 2. Themethod of claim 1 wherein a first portion of the oxygenatedintermediates are recycled to form in part the solvent in step (ii); andprocessing at least a second portion of the oxygenated intermediates toform a liquid fuel.
 3. The method of claim 1 wherein the oxygenatedintermediates is subjected to condensation to produce a liquid fuel. 4.The method of claim 2 wherein the oxygenated intermediates is subjectedto condensation to produce a liquid fuel.
 5. The method of claim 1wherein the oxygenated intermediates is subjected to dehydration andalkylation to produce a liquid fuel.
 6. The method of claim 2 whereinthe oxygenated intermediates is subjected to dehydration and alkylationto produce a liquid fuel.
 7. The method of claim 1 wherein the digestivesolvent comprises (a) at least one alkali selected from the groupconsisting of sodium hydroxide, sodium carbonate, sodium sulfide,potassium hydroxide, potassium carbonate, ammonium hydroxide, andmixtures thereof and (b) water.
 8. The method of claim 2 wherein thedigestive solvent comprises (a) at least one alkali selected from thegroup consisting of sodium hydroxide, sodium carbonate, sodium sulfide,potassium hydroxide, potassium carbonate, ammonium hydroxide, andmixtures thereof, (b) water and (c) oxygenated intermediates.
 9. Themethod of claim 1 wherein the digestive solvent comprises an at leastpartially water miscible organic solvent.
 10. The method of claim 9wherein the organic solvent comprises oxygenated intermediates from step(iii).
 11. The method of claim 1 wherein the pretreated biomass containssoluble carbohydrates and having less than 10% of the sulfur content andless than 10% of the nitrogen content based on untreated biomass on adry mass basis.
 12. A method comprising: (i) providing a biomasscontaining celluloses, hemicelluloses, lignin, nitrogen, and sulfurcompounds; (ii) removing sulfur compounds and nitrogen compounds fromsaid biomass by contacting the biomass with a digestive solvent to forma pretreated biomass containing soluble carbohydrates and having lessthan 35% of the sulfur content and less than 35% of the nitrogen contentbased on untreated biomass on a dry mass basis; (iii) contacting atleast a portion of the pretreated biomass with a recycle solvent streamto form a digested portion of the pulp; (iv) contacting at least aportion of the digested portion of the pulp with an aqueous reformingcatalyst to form a plurality of oxygenated intermediates; and (v) afirst portion of the oxygenated intermediates are recycled to form inpart the recycle solvent in step (iii); and (vi) processing at least asecond portion of the oxygenated intermediates to form a liquid fuel.13. The method of claim 12 wherein the pretreated biomass containssoluble carbohydrates and having less than 10% of the sulfur content andless than 10% of the nitrogen content based on untreated biomass on adry mass basis.
 14. The method of claim 12 wherein the digestive solventcomprises (a) at least one alkali selected from the group consisting ofsodium hydroxide, sodium carbonate, sodium sulfide, potassium hydroxide,potassium carbonate, ammonium hydroxide, and mixtures thereof and (b)water.
 15. The method of claim 12 wherein the digestive solventcomprises (a) at least one alkali selected from the group consisting ofsodium hydroxide, sodium carbonate, sodium sulfide, potassium hydroxide,potassium carbonate, ammonium hydroxide, and mixtures thereof, (b) waterand (c) oxygenated intermediates.
 16. The method of claim 12 wherein thedigestive solvent comprises an at least partially water miscible organicsolvent.
 17. The method of claim 16 wherein the organic solventcomprises oxygenated intermediates from step (iii).
 18. A methodcomprising: (i) providing a biomass containing celluloses,hemicelluloses, lignin, nitrogen, and sulfur compounds; (ii) removingsulfur compounds and nitrogen compounds from said biomass by contactingthe biomass with a digestive solvent to form a pretreated biomasscontaining soluble carbohydrates and having less than 35% of the sulfurcontent and less than 35% of the nitrogen content based on untreatedbiomass on a dry mass basis; (iii) contacting at least a portion of thepretreated biomass with a recycle solvent stream to form a digestedstream; (iv) contacting at least a portion of the digested portion ofthe digested stream directly with hydrogen in the presence of ahydrogenolysis catalyst to form a first intermediate stream; (v) a firstportion of the first intermediate stream is recycled to form in part therecycle solvent in step (iii); (vi) contacting at least a portion of thefirst intermediate stream with an aqueous reforming catalyst to form anoxygenated intermediates stream; and (vii) processing at least a firstportion of the oxygenated intermediates to form a liquid fuel.
 19. Themethod of claim 18 further comprising (viii) a second portion of theoxygenated intermediate stream is recycled to form in part the recyclesolvent in step (iii).
 20. The method of claim 18 wherein the digestivesolvent comprises (a) at least one alkali selected from the groupconsisting of sodium hydroxide, sodium carbonate, sodium sulfide,potassium hydroxide, potassium carbonate, ammonium hydroxide, andmixtures thereof and (b) water.
 21. The method of claim 18 wherein thedigestive solvent comprises (a) at least one alkali selected from thegroup consisting of sodium hydroxide, sodium carbonate, sodium sulfide,potassium hydroxide, potassium carbonate, ammonium hydroxide, andmixtures thereof, (b) water and (c) oxygenated intermediates.
 22. Themethod of claim 18 wherein the digestive solvent comprises an at leastpartially water miscible organic solvent.
 23. The method of claim 22wherein the organic solvent comprises oxygenated intermediates from step(iii).